united agency washington dc 11111 ill i1111 i ill gepa ... · gepa united states office of research...

GEPA

United States Office of Research ana EPA530lR-93/012 June 1993 ?* Environmental Protection Development

Agency Washington DC 20460 , 111 1111 II 11111 11111 Ill I1111 I Ill PB93 - 23 753 5 Technical Resource

Document

Sal id if icatio n/ . Stabilization- and Application to VVaste Materials

tS

EPAISJQIR-93lOlZ Jane 1993

TECHNICAL RESOURCE DOCUMENT SOLIDIFIC ATION/STABILIZATION

AND ITS APPLICATION TO WASTE MATERIALS

by

BA'ITELLE Columbus Division

Columbus, Ohio 43201-2693

work Assignment No. 0-15 Contract No. 68-CO-0003

Charles Mashni Technical Project Monitor:

Waste Minimization, Destruction and Disposal Research Division

Risk Reduction Engineering Laboratory Cincinnati, Ohio 45268

RISK REDUCl'ION ENGINEERING LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT US. ENVIRONMENTAL PR0"ION AGENCY

Cincinnati, Ohio 45268

I

LQ PROTECTED UNDER INTERNATIONAL COPYRIGHT ALL RIGHTS RESERVED. NATIONAL TECHNICAL INFORMATION SERVICE US. DEPARTMENTOF COMMERCE

NOTICE The information contahed in thk document has been funded

wholly or in part by the US. Environmental Protection Agenq d e r Cbturact #68-CO-ooOS with Batelle, Columbus Divirion It has been subjected to the Agency’s peer and ahninistrative review and approved for publication as an EPA Mention of tracie names or commercial promcctS does not constitute endorsement or recommendation for use.

FOREWORD

Today's r a p i d l y developing and changing technologies and i n d u s t r i a l products and p rac t i ces f requent ly ca r ry w i th them the increased generat ion o f mater ia ls tha t , i f improper ly dea l t wi th , can th rea ten both p u b l i c hea l th and the environment. The U.S. Environmental Pro tec t ion Agency (USEPA)is charged by Congress w i t h p ro tec t i ng the Nat ion's land, a i r , and water resources. Under a mandate o f na t iona l environmental laws, t he Agency s t r i v e s t o formulate and implement act ions lead ing t o a compatible balance between improving the q u a l i t y o f l i f e and min imiz ing the r i s k s t o the environment. These laws d i r e c t t he USEPA t o perform research t o de f ine our environmental problems, measure the impacts, and search f o r so lu t ions .

The Risk Reduction Engineering Laboratory (RREL) i s responsib le f o r planning, implementing, and managing research, development, and demonstrat i on programs i n order t o prov ide a u t h o r i t a t i v e and re1 i a b l e in fo rmat ion t h a t can be used by both regu la to rs and the regulated i n t h e i r comnon e f f o r t s t o p ro tec t t h e environment from the hazards o f i n d u s t r i a l and municipal waste. I n add i t ion , RREL i s a lso responsib le f o r coord inat ing and d isseminat ing the l a t e s t engineer ing and s c i e n t i f i c technology developments aimed a t m i t i g a t i n g the harmful e f f e c t s o f environmental contaminants.

Th is Technical Resource Document contains the l a t e s t in fo rmat ion on the use o f solidification/stabilization f o r the treatment o f hazardous waste, assembled f o r EPA by B a t t e l l e i n c lose consu l ta t ion w i t h a d is t ingu ished panel o f exper ts eminently renowned i n t h i s f i e l d . It addresses several issues i nc lud ing such important questions as t o when t h i s technology i s appropr ia te f o r a s p e c i f i c waste and when it i s not . Our goal i s t o prov ide the user community w i t h the most comprehensive informat ion ava i l ab le t o enable them t o manage t h e i r waste i n the most e f f i c i e n t , feas ib le , and safe manner and t o mainta in a harmonious r e l a t i o n s h i p between man and h i s environment.

!

E. Timothy Oppelt, D i r e c t o r Risk Reduction Engineering Laboratory

iii

ABSTRACT

S t a b i l i z a t i o n / s o l i d i f i c a t i o n (S/S) processes are e f f e c t i v e i n

S/S has been i d e n t i f i e d as the Best Demonstrated Ava i l ab le t r e a t i n g a v a r i e t y o f d i f f i c u l t t o manage waste mater ia ls f o r reuse o r disposal . Technology f o r t r e a t i n g a wide range o f Resource Conservation and Recovery Act (RCRA) non-wastewater hazardous waste subcategories. S/S has been se lected as the t reatment technology o f choice f o r 26% o f t he remedial ac t ions complete a t Superfund s i t e s through f i s c a l year 1992.

many S/S processes make the technology appear simple. s i g n i f i c a n t chal lenges t o the successful app l i ca t i on o f S/S processes. The morphology and chemistry o f S/S-treated waste are complex. b inder requ i res an understanding o f the 'chemistry o f t he b u l k ma te r ia l , the contaminants, and the binder. i n t e r a c t i o n s among the var ious components t o ensure e f f i c i e n t and re1 i a b l e resu l t s .

Ba t te l l e , under the d i r e c t i o n o f the U.S. Environmental Pro tec t ion Agency, has prepared t h i s Technical Resources Document (TRD) as a resource f o r t he S/S user community and a guide t o promote the best f u t u r e a p p l i c a t i o n o f S/S processes. , An extensive body o f in fo rmat ion i s ava i l ab le descr ib ing the theory and p r a c t i c e o f S/S processes. combining theory, p rac t ice , and regu la to ry aspects o f S/S a p p l i c a t i o n t o RCRA, Superfund, and s i m i l a r waste mater ia ls . ma te r ia l s i n t o one comprehensive reference.

The TRD i s intended f o r s i t e managers consider ing S/S as an op t i on f o r t r e a t i n g hazardous wastes. responsib le f o r se lec t i on and design o f S/S t reatment methods. about S/S technology i s presented i n d e t a i l e d t e x t desc r ip t i ons supported by summary tab les , check l i s ts , and f igures. It g ives the user a summary o f cu r ren t S/S technology. The technology areas covered a re b inders and t h e i r b ind ing mechanisms, waste in te r fe rences w i t h S/S processes, S/S t reatment o f organic contaminants, a i r emissions f o r S/S processes, leach ing mechanisms, long- term s t a b i l i t y , reuse and disposal o f S/S-treated waste, and economics. In fo rmat ion i s a lso prov ided t o c l a r i f y t he l i m i t a t i o n s o f S/S technology and ongoing research t o f u l f i l l f u t u r e development needs.

Contract t68-CO-0003 w i t h Ba t te l l e , Columbus, under sponsorship o f t he USEPA. It covers a per iod from 11/01/90 through 05/30/92.

The standard b u l k mater ia l handl ing and mix ing equipment used i n However, there are

Se lec t ion o f the

The S/S user must be fu l l y aware o f t he complex

However, no one document ex i s ted

Th is TRD p u l l s a d i ve rse range o f

I t prov ides technology t r a n s f e r t o persons In fo rmat ion

This TRD was submitted i n f u l f i l l m e n t o f Work Assignment 0-15 o f

a

iv

CONTENTS

m NOTICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i v TABLES xv FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x v i i ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x v i i i

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I I

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.1 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1 .1 .1 D e f i n i t i o n o f S o l i d i f i c a t i o n and S t a b i l i z a t i o n . . . . . 1-2 1.1.2 P o s i t i o n o f S/S i n t he U.S. EPA Environmental

Management Options Hierarchy . . . . . . . . . . . . . . 1-2 1.1.3 A p p l i c a t i o n o f Solidification/Stabilization . . . . . . 1-4

1.2 PURPOSE AND SCOPE . . . . . . . . . . . . . . . . . . . . . . . 1-11

1.2.1 Objec t ives . . . . . . . . . . . . . . . . . . . . . . . 1-11 1 .2 .2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . 1-13

1.2.2.1 Waste Types . . . . . . . . . . . . . . . . . .. 1-13 1.2.2.2. Processes . . . . . . . . . . . . . . . . . . 1-13

1.2.3 Audience 1-14

1.2.3.1 CERCLA App l ica t ions . . . . . . . . . . . . . . 1-14 1.2.3.2 RCRA App l i ca t i ons . . . . . . . . . . . . . . . 1-15

. . . . . . . . . . . . . . . . . . . . . . . . I

. . . . . . . . . . . . . . . . . . . 1 1.3 REGULATORY CONSIDERATION 1-15

1.3.1 Regulatory Framework . . . . . . . . . . . . . . . . . . 1-15 1.3.2 RCRA land Disposal R e s t r i c t i o n s . . . . . . . . . . . . 1-16 1.3.3 A p p l i c a t i o n o f Land Disposal R e s t r i c t i o n s

t o CERCLA S i t e s . . . . . . . . . . . . . . . . . . . . 1-19 1.3.4 Toxic Substances Control Act . . . . . . . . . . . . . . 1-21 1.3.5 Other Environmental Regulat ions . . . . . . . . . . . . 1-22

2 SOlIDIFICATION/STABILIZATION (S/S) TECHNOLOGY SCREENING PROCEDURES . 2-1

2 .1 INTROOUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.1.2 The Need for T r e a t a b i l i t y Studies . . . . . . . . . . . 2-3

CONTENTS (Continued) e

2.2 SITE-SPECIFIC BASELINE INFORMATION REQUIREMENTS . . . . . . . . 2-5 2.2.1 Waste Sampling . . . . . . . . . . . . . . . . . . . . . 2-5

2.2.1.1 Composites vs . Hot Spots . . . . . . . . . . . 2-5 2.2.1.2 Statistical Approaches . . . . . . . . . . . . 2-9

2.2.2 Waste Acceptance . . . . . . . . . . . . . . . . . . . . 2-12 2.2.3 Waste Characterization . . . . . . . . . . . . . . . . . 2-13

2.2.3.1 Regul atory Framework . . . . . . . . . . . . . 2-15 2.2.3.2 Contaminant Characteristics & Treatment Types . 2-16 2.2.3.3 Sampling and Analysis . . . . . . . . . . . . . 2-21

2.2.4 Site Characterization . . . . . . . . . . . . . . . . . 2-25 2.2.6 Guidance for Site-Specific Information Requirements . . 2-28 2.2.5 Quality Assurance/Quality Control . . . . . . . . . . . 2-27

2. 3 PERFORMANCE OBJECTIVES . . . . . . . . . . . . . . . . . . . . 2-28

2.3.1 Regulatory Requirements . . . . . . . . . . . . . . . . 2-33 2.3.1.1 CERCLA . . . . . . . . . . . . . . . . . . . . 2-34 2.3.1.2 RCRA . . . . . . . . . . . . . . . . . . . . . 2-40

2.3.2 Technical and Institutional Requirements . . . . . . . . 2-43 2.3.3 Approach for Setting Performance Criteria . . . . . . . 2-43

2.4 INITIAL TECHNOLOGY SCREENING . . . . . . . . . . . . . . . . . 2-46 2.4.1 Technology Screening/Feasibility Study Process . . . . . 2-47

2.4.1.1 CERCLA Technology Screening . . . . . . . . . . 2-47 2.4.1.2 Technology Screening at RCRA TSD Facilities . . 2-51

2.4.2 General Criteria for Not Using S/S . . . . . . . . . . . 2-51 2.4.3 Outcome o f Technology Screening . . . . . . . . . . . . 2-51

2.5 WASTE/BINDER COMPATIBILITY LITERATURE SCREENING . . . . . . . . 2-56 2.5.1 Identify Available Binders . . . . . . . . . . . . . . . 2-56 2.5.2 Screening Process . . . . . . . . . . . . . . . . . . . 2-56

2.5.2.1 Interferences and Chemical Incompatibilities . 2-58 2.5.2.2 Metal Chemistry Considerations . . . . . . . . 2-58 2.5.2.3 Organic Chemistry Considerations for Target .

Contaminants . . . . . . . . . . . . . . . . . 2-59 2.5.2.4 Compatibility with the Disposal

or Reuse Environment . . . . . . . . . . . . . 2-59 2.5.2.5 Cost . . . . . . . . . . . . . . . . . . . . . 2-60 2.5.2.6 Process Track Record . . . . . . . . . . . . . 2-60

vi

CONTENTS (Continued)

2.6 LABORATORY BENCH-SCALE SCREENING OF THE UASTE/BINDER MIXTURES . 2-61 I 2.6.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . 2-61 2.6.2 Approach . . . . . . . . . . . . . . . . . . . . . . . . 2-62

2.6.2.1 Experimental Design . . . . . . . . . . . . . . 2-62 2.6.2.2 Performance Tes t i ng . . . . . . . . . . . . . . 2-64

2.6.3 Technical Guidance . . . . . . . . . . . . . . . . . . . 2-66

2.7 BENCH-SCALE PERFORMANCE TESTING/PROCESS OPTIMIZATION . . . . . 2-66

2.7.1 Purpose and Object ives . . . . . . . . . . . . . . . . . 2-66 2.7.2 How Much Performance Test ing? . . . . . . . . . . . . . 2-70

2.7.2.1 Levels of Risk . . . . . . . . . . . . . . . . 2-70 2.7.2.2 Levels o f Performance Tes t i ng . . . . . . . . . 2-70 2.7.2.3 Tests f o r S p e c i f i c B ind ing Agents . . . . . . . 2-74 2.7.2.4 Acceptance C r i t e r i a . . . . . . . . . . . . . . 2-74 2.7.2.5 Process Opt imizat ion . . . . . . . . . . . . . 2-75

2.7.3 Technical Guidance . . . . . . . . . . . . . . . . . . . 2-76

2.8 PILOT-SCALE AND FIELD DEMONSTRATIONS . . . . . . . . . . . . . 2-76 I I 2.8.1 The Need fo r Process Scale-up . . . . . . . . . . . . . 2-76 2.8.2 Scale-up Issues . . . . . . . . . . . . . . . . . . . . 2-81

2.8.2.1 Waste Excavation and Handl ing . . . . . . . . . 2-82 2.8.2.2 S t a b i l i z i n g Agent Storage . . . . . . . . . . . 2-83 2.8.2.3 Pretreatment of Waste . . . . . . . . . . . . . 2-83 2.8.2.4 M ix ing and Curing . . . . . . . . . . . . . . . 2-83 2.8.2.5 S t a b i l i z e d Waste Disposal . . . . . . . . . . . 2-85

2.8.3 Sampling and Analys is o f t h e Treated Waste . . . . . . . 2-85

3 S/S PROCESS PERFORMANCE TESTS . . . . . . . . . . . . . . . . . . . 3-1

3.1 PHYSICAL TESTS . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1.1 General Proper ty Tests . . . . . . . . . . . . . . . . . 3-2

3.1.1.1 Mois ture Content . . . . . . . . . . . . . . . 3-2 3.1.1.2 P a r t i c l e S i z e Analys is . . . . . . . . . . . . 3-2 3.1.1.3 S p e c i f i c G r a v i t y . . . . . . . . . . . . . . . 3-2 3.1.1.4 Suspended So l i ds . . . . . . . . . . . . . . . 3-8 3.1.1.5 Pa in t F i l t e r Test . . . . . . . . . . . . . . . 3-8 3.1.1.6 L i q u i d Release Test (LRT) . . . . . . . . . . . 3-8 3.1.1.7 A t te rbe rg L i m i t s . . . . . . . . . . . . . . . 3-8 3.1.1.8 Visual Observation . . . . . . . . . . . . . . 3-9

vi i

3.1.2 3.1.3 3.1.4 3.1.5 3.1.6

3.1.7 3.1.8

CONTEWTS (Continued)

Bulk Densi ty Tests . . . . . . . . . . . . . . . . . . . 3-9 Compaction Tests . . . . . . . . . . . . . . . . . . . . 3-9 Permeabi l i ty (Hydraul ic Conduct iv i ty ) Tests . . . . . . 3-9 Poros i t y Tests . . . . . . . . . . . . . . . . . . . . . 3-10 Strength Tests . . . . . . . . . . . . . . . . . . . . . 3-10

3.1.6.2 Immersion Compressive Strength . . . . . . . . 3-11 3.1.6.3 T r i a x i a l Compression . . . . . . . . . . . . . 3-11 3.1.6.4 Flexura l St rength . . . . . . . . . . . . . . . 3-11 3.1.6.5 Cone Index . . . . . . . . . . . . . . . . . . 3-11 General Concrete/Soil-Cement Tests . . . . . . . . . . . 3-12 D u r a b i l i t y Test ing . . . . . . . . . . . . . . . . . . . 3-12

3.1.6.1 Unconfined Compressive Strength (UCS) . . . . . 3-10

3.2 LEACHING/EXTRACTION TESTS . . . . . . . . . . . . . . . . . . . 3-13 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 3.2.10 3.2.11 3.2.12 3.2.13 3.2.14

3.2.15 3.2.16

T o x i c i t y Charac te r i s t i c Leaching Procedure (TCLP) . . . 3-19 Ex t rac t i on Procedure T o x i c i t y (EP Tox) Test . . . . . . 3-20 TCLP "Cage" Mod i f i ca t i on . . . . . . . . . . . . . . . 3-20 . . . . . . 3-20 M u l t i p l e Ex t rac t i on Procedure (MEP) . . . . . . . . . . 3-21 Synthet ic Ac id P r e c i p i t a t i o n Leach Test . . . . . . . . 3-21 Monof i l led Waste E x t r a c t i o n Procedure (WEP) . . . . . 3-22 American Nuclear Society Leach Test (ANSI/ANS/16.1) . . 3-22 Dynamic Leach Test (DLT) . . . . . . . . . . . . . . . 3-22 Shake Ex t rac t i on Test . . . . . . . . . . . . . . . . . 3-23 . . . . . . . . . . . . . 3-23

C a l i f o r n i a Waste Ex t rac t i on Test (Cal YET)

Equ i l i b r i um Leach Test (ELT) Sequential Ex t rac t i on Test (SET) . . . . . . . . . . . . 3-23 Sequential Chemical Ex t rac t i on (SCE) . . . . . . . . . 3-23 S t a t i c Leach Test Method (Ambient- and High -Temperature) . . . . . . . . . . . . . . . . . . . 3-24 Agi ta ted Powder Leach Test Method . . . . . . . . . . . 3-24 Soxhlet Leach Test Method . . . . . . . . . . . . . . . 3-24

3.3 CHEMICAL TESTS AND ANALYSES . . . . . . . . . . . . . . . . . . 3-25 3.3.1 3.3.2 3.3.3 3.3.4 3.3.5 3.3.6 3.3.7 3.3.8 3.3.9 3.3.10 3.3.11 3.3.12 3.3.13 3.3.14

pH . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25 Oxidation/Reduction Poten t ia l (Eh) . . . . . . . . . . 3-25 Major Oxide Components . . . . . . . . . . . . . . . . 3-30 Tota l Organic Carbon (TOC) . . . . . . . . . . . . . . 3-30 Oil and Grease . . . . . . . . . . . . . . . . . . . . 3-30 E l e c t r i c a l Conduct iv i t y . . . . . . . . . . . . . . . . 3-30 Acid Neu t ra l i za t i on Capacity (ANC) . . . . . . . . . . 3-31 A l k a l i n i t y . . . . . . . . . . . . . . . . . . . . . . 3-31 Tota l Dissolved So l ids (TDS) . . . . . . . . . . . . . 3-31 Reactive Cyanide and S u l f i d e . . . . . . . . . . . . . 3-32 R e a c t i v i t y o f S i l i c a Aggregates . . . . . . . . . . . . 3-32 Metal Analys is . . . . . . . . . . . . . . . . . . . . 3-32

Base. Neutra l . and Acid (BNA) Organic Compounds . . . . 3-33 V o l a t i l e Organic Compounds . . . . . . . . . . . . . . 3-32

viii


3.3.15 Polychlor inated Biphenyls (PCBs) . . . . . . . . . . . 3-33 3.3.16 Other Contaminant Analyses . . . . . . . . . . . . . . 3-34 3.3.17 Anion Measurements . . . . . . . . . . . . . . . . . . 3-34 3.3.18 I n te r fe ran ts Screen . . . . . . . . . . . . . . . . . . 3-34

3.4 BIOLOGICAL TESTS . . . . . . . . . . . . . . . . . . . . . . . 3-34 3 .5 MICROCHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . 3-36

3 .5 .1 X-Ray D i f f r a c t i o n . . . . . . . . . . . . . . . . . . . 3-37 3 . 5 . 2 Four ier Transform I n f r a r e d (FTIR) Spectroscopy . . . . . 3-37 3.5.3 Scanning Electron Microscopy (SEM) and

Energy-Dispersive X-ray Analysis (EDXA) . . . . . . . . 3-38 3.5.4 Nuclear Magnetic Resonance (NMR) Spectroscopy . . . . . 3-38 3.5.5 Opt ica l Microscopy . . . . . . . . . . . . . . . . . . . 3-38

4 STATUS OF SOLIOIFICATION/STABILIZI~ TECHNOLOGY . . . . . . . . . 4-1

4 . 1 S/S PROCESSES AND BINDERS . . . . . . . . . . . . . . . . . . . 4-2

4.1.1 Inorganic Binders . . . . . . . . . . . . . . . . . . . 4-3

4.1.1.1 Cement Processes . . . . . . . . . . . . . . . 4-4 4.1.1.2 Pozzolanic Processes . . . . . . . . . . . . . 4-7 4.1.1.3 E t t r i n g i t e Formation E f f e c t s . . . . . . . . . 4-8

4.1.2 Organic Binders . . . . . . . . . . . . . . . . . . . . . 4.9

4 .1 .2 .1 Thermoplastic Processes . . . . . . . . . . . . 4-11 4.1.2.2 T h e m s e t t i n g Processes . . . . . . . . . . . . 4-12

4.1.3 Addi t ives . . . . . . . . . . . . . . . . . . . . . . . 4-12 4.1.4 Pretreatment . . . . . . . . . . . . . . . . . . . . . . 4-14

4.1.4.1 Adjustment o f Physical Charac te r i s t i cs . . . . 4-14 4.1.4.2 Pretreatment o f Inorganic Const i tuents . . . . 4-14 4.1.4.3 Pretreatment of Organic Const i tuents . . . . . 4-15 4.1.4.4 Treatment Trains Invo lv ing S/S . . . . . . . . 4-15

4 .2 IMMOBILIZATION MECHANISMS . . . . . . . . . . . . . . . . . . . 4-16

4.2.1 Physical Mechanisms . . . . . . . . . . . . . . . . . . 4-16 4.2.2 Chemical Mechanisms . . . . . . . . . . . . . . . . . . 4-18

4.2.2.1 Inorganic Wastes . . . . . . . . . . . . . . . 4-18

4.2.2.1.1 Basic Chemical E q u i l i b r i a . . . . . 4-18 4.2.2.1.2 E f f e c t o f A l k a l i n e Condit ions . . . 4-21 4.2.2.1.3 E f f e c t o f Redox Poten t ia l . . . . . 4-22

COMTENTS (Continued)

4.2.2.1.4 Metal S i l i c a t e s . . . . . . . . . . 4-25 4.2.2.1.5 Other Low S o l u b i l i t y Phases . . . . 4-26

4.2.2.2 Organic Wastes . . . . . . . . . . . . . . . . 4-27

4.2.3 Concept o f Surface Seal ing . . . . . . . . . . . . . . . 4-28

4.3 POTENTIAL INTERFERENCES . . . . . . . . . . . . . . . . . . . . 4-29

4.3.1 In ter ferences w i t h S o l i d i f i c a t i o n . . . . . . . . . . . 4-30 4.3.2 In te r fe rences w i t h S t a b i l i z a t i o n . . . . . . . . . . . . 4-30

ISSUES DEALING WITH THE STABILIZATION OF ORGANIC WASTES

4.4.1 I n t roduc t i on . . . . . . . . . . . . . . . . . . . . . . 4-39 4.4.2 S/S Addi t i ves Compatible w i t h Organics . . . . . . . . . 4-40 4.4.3 Approach t o Evaluat ing F e a s i b i l i t y o f S/S

4.4.3.1 Dest ruc t ive o r Removal Technologies Versus S/S . . . . . . . . . . . . . . . . . . 4-48

4.4.3.2 V o l a t i l e Organic Contaminants . . . . . . . . . 4-48 4.4.3.3 Nonpolar Organic Contaminants . . . . . . . . . 4-49 4.4.3.4 Degradation and By-product Formation . . . . . 4-50

4.5 A I R EMISSIONS AND CONTROL . . . . . . . . . . . . . . . . . . . 4-50

4.5.1 V o l a t i l e Organic Compounds . . . . . . . . . . . . . . . 4-51 4.5.2 Par t i cu la tes and Other Emissions . . . . . . . . . . . . 4-52 4.5.3 C o n t r o l l i n g A i r Emissions . . . . . . . . . . . . . . . 4-52 4.5.4 Sign i f i cance of t he Amended Clean A i r Act . . . . . . . 4-53

4.6 LEACHING MECHANISMS . . . . . . . . . . . . . . . . . . . . . . 4-54

4 .4 AND OF MIXED ORGANIC AND INORGANIC WASTES . . . . . . . . . . . 4-39

f o r Wastes Containing Organics . . . . . . . . . . . . . 4-45

4.6.1 Leaching Associated w i t h Inorganic S/S Processes . . 4.6.2 Leaching Associated w i t h Organic S/S Binders . . . . 4.6.3 Leaching Models . . . . . . . . . . . . . . . . . .

4.6.3.1 Disso lu t i on /D i f f us ion K i n e t i c s . . . . . . 4.6.3.1.1 Nonporous Sol i d . . . . . . . . 4.6.3.1.2 Porous S o l i d . . . . . . . . . .

4.6.3.2 Examples o f Ex i s t i ng Models . . . . . . . . 4.6.3.3 The Moving Boundary o r Shr ink ing Core Model

. . 4-55 . . 4-58 . . 4-58

. . 4-58

. . 4-59 . . 4-61

. . 4-63 . . 4-66

X


4.7 LONG-TERM PERFORMANCE . . . . . . . . . . . . . . . . . . . . . 4-66 4.7.1 Field Studies . . . . . . . . . . . . . . . . . . . . . 4-67 4.7.2 Laboratory Studies . . . . . . . . . . . . . . . . . . . 4-68 4.7.3 Modeling . . . . . . . . . . . . . . . . . . . . . . . . 4-69

4.8 USE/REUSE VERSUS DISPOSAL . . . . . . . . . . . . . . . . . . . 4-70 4.8.1 Alternatives . . . . . . . . . . . . . . . . . . . . . . 4-70 4.8.2 Limitations . . . . . . . . . . . . . . . . . . . . . . 4-73 4.8.3 Compatibility With the Disposal Environment . . . . . . 4-73

4.9 COST INFORMATION . . . . . . . . . . . . . . . . . . . . . . . 4-74

4.9.1 Treatability Study Costs . . . . . . . . . . . . . . . . 4-75 4.9.1.1 Waste Characterization and Establ ishing

4.9.1.2 Bench-Scale Testing and Analysis . . . . . . . 4-75 4.9.2 Full-scale Remediation Costs . . . . . . . . . . . . . . 4-77

4.9.2.1 Planning . . . . . . . . . . . . . . . . . . . 4-77 4.9.2.2 Mobilization and Demobilization . . . . . . . . 4-78 4.9.2.3 Treatment . . . . . . . . . . . . . . . . . . . 4-78 4.9.2.4 Final Disposal . . . . . . . . . . . . . . . . 4-82

Performance Objectives . . . . . . . . . . . . 4-75

4.9.3 Estimates o f Stabilization Costs . . . . . . . . . . . . 4-82 4.9.4 Case Study . . . . . . . . . . . . . . . . . . . . . . . 4-84

TECHNOLOGY SHORTCOMINGS AND LIMITATIONS . . . . . . . . . . . . . . 5-1 5.1 PROCESS/BINDER CONSIDERATIONS . . . . . . . . . . . . . . . . . 5-1

5.1.1 Hierarchy o f Waste Management . . . . . . . . . . . . . 5-1 5.1.2 Scale-up Uncertainties . . . . . . . . . . . . . . . . . 5-1 5.1.3 Proprietary Binders . . . . . . . . . . . . . . . . . . 5-1 5.1.4 Binder "Overkill' . . . . . . . . . . . . . . . . . . . 5-2

5.2 WASTE FORM/CONTAMINANT ISSUES . . . . . . . . . . . . . . . . . 5-2 5.2.1 Cornpl ications o f Physicochemical Form

5-2 5.2.2 Interferences and Incompatibilities . . . . . . . . . . 5-2 5.2.3 Volatile Organic Contaminants . . . . . . . . . . . . . 5-3 5.2.4 Multicontaminant Wastes . . . . . . . . . . . . . . . . 5-4

o f the Target Contaminants . . . . . . . . . . . . . . .


5.2.5 Weaknesses o f Cement-Based Waste Forms . . . . . . . . . 5-4 5.2.6 Sample Heterogenei ty . . . . . . . . . . . . . . . . . . 5-5

5.3 TREATABILITY AND PERFORMANCE TESTING ISSUES . . . . . . . . . . 5-5

5.3.1 Test ing L im i ta t i ons . . . . . . . . . . . . . . . . . . 5-5 5.3.2 Long-Term Performance . . . . . . . . . . . . . . . . . 5-7 5.3.3 Reproduc ib i l i t y . . . . . . . . . . . . . . . . . . . . 5-8 5.3.4 L im i ta t i ons i n S/S T r e a t a b i l i t y Reference Data . . . . . 5-8

6 CURRENT RESEARCH AND FUTURE DEVELOPMENT NEEDS . . . . . . . . . . . 6-1

6.1 CURRENT RESEARCH . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.1.1 Binders . . . . . . . . . . . . . . . . . . . . . . . . 6-1

o f Hazardous Substances . . . . . . . . . . . . 6-1

Wastes by S i l i c a Fume ( M i c r o s i l i c a ) Concrete . 6-1 Physical and Chemical Aspects o f I nmob i l i za t i on . . . . 6-1

o f RCRA/CERCLA Wastes . . . . . . . . . . . . . 6-2

Experimental Study o f S/S Treatment

Improvement i n S/S Treatment o f Hazardous Inorganic

Eva1 ua t i on o f Sol i d i f i cat ion /Stab i l i z a t i o n

6.1.2 Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 6-2

Review and Analys is o f T r e a t a b i l i t y Data Invo lv ing S/S Treatment o f S o i l s . . . . . . . 6-2

Morphology and Microchemistry o f S/S-Treated Waste . . . 6-2 Fate o f PCBs i n S o i l Fol lowing S t a b i l i z a t i o n

w i t h Quick l ime . . . . . . . . . . . . . . . . 6-3 S/S Treatment o f Sa l t s o f As. Cd. Cr . and Pb . . . . . . 6-3 The Nature o f Lead. Cadmium. and Other Elements i n

i n Inc ine ra t i on on Residues and The i r S t a b i l i z e d Products . . . . . . . . . . . 6-3

6.1.3 In te r fe rences . . . . . . . . . . . . . . . . . . . . . 6-4

Factors A f f e c t i n g the S/S Treatment o f Toxic Waste . . . 6-4 E f f e c t s o f Selected Waste Const i tuents

on S/S-Treated Waste Leachab i l i t y . . . . . . . 6-4

6.1.4 Organics and A i r Emissions . . . . . . . . . . . . . . . 6-4

Roles o f Organic Compounds i n S o l i d i f i c a t i o n / S t a b i l i - za t i on o f Contaminated S o i l s . . . . . . . . . 6-4

Measurement o f V o l a t i l e Emissions from S/S-Treated Waste . . . . . . . . . . . . 6-5

xii


F i e l d Assessment o f A i r Emissions from Hazardous Waste S/S Processing . . . . . . 6-5

SJS Treatment o f Metal Wastes Contaminated w i t h V o l a t i l e Organics . . . . . . . . . . . . 6-5

Immobi l izat ion of Organics i n S/S Waste Forms . . . . . 6-5

6 .1 .5 Test Methods . . . . . . . . . . . . . . . . . . . . . . 6-5

Method Development . . . . . . . . . . . . . . . . . . . 6-5 I nves t i ga t i on o f Test Methods f o r S o l i d i f i e d Waste . . . 6-6 C r i t i c a l Charac ter is t i cs o f Hazardous

S/S-Treated Waste . . . . . . . . . . . . . . . 6-6 Advanced Test Methods . . . . . . . . . . . . . . . . . 6-6 Assessment o f Long-Term D u r a b i l i t y o f

So l i d i f i ed /S tab i l i zed Hazardous Waste Forms - Lab Component and F i e l d Component . . . . . . . 6-7

6.1.6 Leaching and Transport Models . . . . . . . . . . . . . 6-7

Contaminant P r o f i l e Analys is . . . . . . . . . . . . . . 6-7 The Binding Chemistry and Chemical Leaching Mechanism

o f Hazardous Substances i n Cementit ious S/S Binders . . . . . . . . . . . 6-7

Development o f a Numerical Three-Dimensional Leaching Model . . . . . . . . . . . . . . . . 6-8

Ac id Leaching Rate and Advancement of Acid Front i n S/S-Treated Waste . . . . . . 6-8

Leaching Test Methods and Models . . . . . . . . . . . . 6-8 Review and Analysis o f T r e a t a b i l i t y Data Invo lv ing

Solidification/Stabilization o f S o i l s . . . . . 6-9

6 .1 .7 Compat ib i l i t y w i t h Disposal o r Reuse . . . . . . . . . . 6-9

Assessment o f long-Term D u r a b i l i t y o f S/S-Treated Waste . . . . . . . . . . . . . 6-9

E f f e c t o f Curing Time on Leaching . . . . . . . . . . . 6-9 F i e l d Performance o f S/S-Treated Waste . . . . . . . . . 6-10 U t i l i z a t i o n and Disposal . . . . . . . . . . . . . . . . 6-10

6.1.8 T r e a t a b i l i t y Tests and S/S Process App l i ca t i on . . . . . 6-10

Superfund Innovat ive Technology Evaluation (SITE) Program . . . . . . . . . . . 6-10

Munic ipa l Waste Combustion Residue S/S Program . . . . . 6-10 Leaching Mechanisms and Performance o f S/S-Treated

Hazardous Waste Substances i n Mod i f ied Cementit ious and Polymeric Matr ices . . . . . . 6-12

S t a b i l i z a t i o n Poten t ia l o f Lime I n j e c t i o n Mu1 t i s tage Burner (LIMB) Product Ash

xiii


Used with Hazardous Distillation Residues . . . 6-12

in a Shore Protection Device . . . . . . . . . 6-12 Stabilized Incinerator Residue

6.2 FUTURE DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . 6-13

6 .2 .1 6 .2 .2 6 .2 .3 6.2.4 6.2.5 6.2.6 6.2.7 6.2.8

Binders . . . . . . . . . . . . . . . . . . . . . . . . 6-13 Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 6-13 Interferences . . . . . . . . . . . . . . . . . . . . . 6-14 Organics and Air Emissions . . . . . . . . . . . . . . . 6-14 Test Methods . . . . . . . . . . . . . . . . . . . . . . 6-14 Leaching and Transport Models . . . . . . . . . . . . . 6-15 . . . . . . . . . . 6-15 . . . . . . . . . 6-16 Compatibility with Disposal or Reuse Treatability Tests and S/S Application

7 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 1

APPENDIX A: SOLIDIFICATION/STABLILIZATION TECHNOLOGY SCREENING WORKSHEETS . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B: DRAFT REPORT: SAMPLIN6 AND ANALYTICAL PROCEDURES . . . . . . B-1

APPENDIX C: GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

XiV


TABLES

TABLE 1-1. RCRA WASTES FOR WHICH SOLIDIFICATION/STABILIZATION I S IDENTIF IED AS BEST DEMONSTRATED I AVAILABLE TECHNOLOGY (BDAT) . . . . . . . . . . . . . . . . . 1-5

GENERAL INDUSTRIAL WASTE CATEGORIES . . . . . . . . . . . . . 2-14 TABLE 2-1. I TABLE 2-2. EXAMPLES OF SOME METAL WASTES TESTED FOR

SOL IDIFICATION/STAB I L IZATION TREATMENT . . . . . . . . . . . 2 . 17

TABLE 2-3. EXAMPLES OF SOHE METAL AND ORGANIC MIXED WASTES TESTED FOR SOLIDIFICATION/STABILIZATION TREATMENT . . . . . . 2-19

EXAMPLES OF SOME ORGANIC MlXED WASTES TESTED FOR SOLIDIFICATION/STABILIZATION TREATMENT . . . . . . . . . 2-20

EXAMPLES OF OTHER INORGANIC WASTES TESTED FOR SOL ID1 F I CATION/STABIL IZATION TREATMENT . . . . . . . . . . . 2- 22

TABLE 2-6. GUIDANCE FOR COLLECTING BASELINE INFORHATION . . . . . . . . 2-29

TABLE 2-7.

TABLE 2-4.

TABLE 2-5.

ALTERNATIVE TREATMENT LEVELS FOR SOIL AND DEBRIS CONTAMINATED WITH RESTRICTED RCRA HAZARDOUS WASTES . . . . . 2-36

TABLE 2-8. EXAMPLES OF REGULATORY ARARs . . . . . . . . . . . . . . . . 2-40

TABLE 2 -9 . TOXICITY CHARACTERISTIC CONSTITUENTS AND REGULATORY LEVELS . . . . . . . . . . . . . . . . . . . . 2-41

TABLE 2-10. EXAMPLES OF TREATABILITY PERFORMANCE OBJECTIVES BASED ON NONREGULATORY FACTORS . . . . . . . . . . 2-44

TABLE 2 - 11. APPL 1 CAB I L I T Y OF SOL I D 1 F ICAT I ON/STAB I L I U T ION TO SITE-SPECIFIC WASTE . . . . . . . . . . . . . . . . . . . 2-54

TABLE 2-12. BENCH-SCALE BINDER SCREENING GUIDANCE . . . . . . . . . . . . 2-67

TABLE 2-13. RISK FACTORS FOR EVALUATING LEVELS OF PERFORMANCE TESTING . . . . . . . . . . . . . . . . . . . . . 2-71

TABLE 2-14. LEVELS OF PERFORMANCE TESTING AND EXAMPLE TESTING REQUIREMENTS . . . . . . . . . . . . . . . . . . . . 2-73

TABLE 2-15. GUIDANCE FOR BENCH-SCALE PERFORMANCE TESTING . . . . . . . . 2-77

TABLE 3-1. PHYSICAL TESTS . . . . . . . . . . . . . . . . . . . . . . . 3-3

TABLE 3-2. LEACHING/EXTRACTION TESTS . . . . . . . . . . . . . . . . . . 3-14

TABLE 3.3 . TABLE 3.4 . TABLE 3.5 . TABLE 3.6 . TABLE 4.1 . TABLE 4.2 . TABLE 4.3 .

TABLE 4.4 . TABLE 4.5 .

TABLE 4.6 .

TABLE 4.7 . TABLE 4.8 . TABLE 4.9 .

CONTENTS ( C o n t i n u e d )

EXTRACTION CONDITIONS . . . . . . . . . . . . . . . . . . . . 3-16

CHEMICAL TESTS . . . . . . . . . . . . . . . . . . . . . . . 3 - 2 6

BIOLOGICAL TESTS . . . . . . . . . . . . . . . . . . . . . . 3 - 3 5

MICROCHARACTERIZATION TESTS . . . . . . . . . . . . . . . . . 3-37

. . . . . . . . . 4 - 1 9

. . . . . . . 4 - 2 4

SUBSTANCES THAT MAY AFFECT CEMENT REACTIONS: I N H I B I T I O N AND PROPERTY ALTERATION . . . . . . . . . . . . . 4 - 3 1

SUMMARY OF FACTORS THAT MAY INTERFERE WITH SOLIDIFICATION/STABILIZATION PROCESSES . . . . . . . . . 4-33

POTENTIAL CHEMICAL INCOMPATIBILITIES BETWEEN BINDER AND WASTE CONSTITUENTS . . . . . . . . . . . . . . . . 4-38

S/S PROCESSES TESTED ON OR APPLIED TO ORGANIC-CONTAINING WASTES . . . . . . . . . . . . . . . . 4 - 4 1

COSTS OF TYPICAL ANALYTICAL TESTS OF UNTREATED AND TREATED WASTES . . . . . . . . . . . . . . . . 4 - 7 6

COSTS OF TYPICAL STABIL IZATION CHEMICALS . . . . . . . . . . 4 - 7 9

COMPARISON OF MAJOR COST ELEMENTS OF SOLIDIFICATION/STABILIZATION WITH CEMENT . . . . . . . . . . 4-80

PK.. VALUES FOR SELECTED METAL PRECIPITATES

pK.. VALUES FOR SELECTED As AND Se PRECIPITATES

TABLE 4.10 . ESTIMATED TREATMENT COSTS MENTIONED I N THE RODS FOR SUPERFUND SITES WHERE STABILIZATION HAS BEEN SELECTED AS A COMPONENT OF THE REMEDIAL ACTION . . . . . . . 4-83

TABLE 4.11 . STABILIZATION COSTS FOR AN 1,800.CUBI C.YARD S I T E CONTAMINATED WITH LEAD . . . . . . . . . . . . . . . . . . . 4-85

SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION PROGRAM: SOLIDIFICATION/STABILIZATION TECHNOLOGIES . . . . . 6-11

WORKSHEETS . . . . . . . . . . . . . . . . . . . . . . . . . A - 4

TABLE A-2 SUMMARY SHEET . . . . . . . . . . . . . . . . . . . . . . . . A-23

TABLE 6- 1

TABLE A - 1 SOLIDIFICATION/STABILIZATION TECHNOLOGY SCREENING

mi

CONTENTS ( C o n t i n u e d )

FIGURES

FIGURE 1-1. U.S. ENVIRONMENTAL PROTECTION AGENGY'S HIERARCHY OF HAZARDOUS WASTE MANAGEMENT . . . . . . . . . . . . . . . . 1-3

FIGURE 2-1. S/S TECHNOLOGY SCREENING . . . . . . . . . . . . . . . . . . 2-2

FIGURE 2-2. INFORMATION COLLECTION STEPS I N THE TECHNOLOGY-SCREENING PROCESS . . . . . . . . . . . . . . . . 2-6

. . . . . . . . . . . 2-50 FIGURE 2-3. GENERAL TECHNOLOGY SCREENING PROCEDURE

FIGURE 2-4. DETERMINING WHETHER S/S IS APPLICABLE AT A RCRA TSD FACIL ITY . . . . . . . . . . . . . . . . . . . . . . 2-52

FIGURE 2-5. S/S DECISION TREE AT A RCRA TSD FACIL ITY . . . . . . . . . . 2-53

FIGURE 2-6. WASTE/BINDER COMPATIBILITY LITERATURE SCREENING . . . . . . . 2-57

FIGURE 2-7. LABORATORY SCREENING OF WASTE/BINDER MIXTURES . . . . . . . . 2-63

FIGURE 2-8. BENCH-SCALE PERFORMANCE TESTING OF SELECTED WASTE/BINDER MIXTURES . . . . . . . . . . . . . . . . . . . . 2-68

FIGURE 2-9. PILOT-SCALE TEST SCREENING . . . . . . . . . . . . . . . . . 2-80

FIGURE 4-1. PROGRESS OF CEMENTATION REACTIONS . . . . . . . . . . . . . . 4-10

FIGURE 4-2. GENERAL DECISION TREE FOR S/S APPLIED TO ORGANIC

a v

CONTAHINANTS. . . . . . . . . . . . . . . . . . . . . . . . . 4-46

FIGURE 4-3. SCHEMATIC ILLUSTRATION OF CONCENTRATION PROFILES, C ( X ) , CHARACTERISTIC OF SPECIES DISSOLVING FROM A NONPOROUS SOLID INTO AN AQUEOUS MEDIUM, WITH x BEING THE DISTANCE INTO THE SOLUTION MEASURED FROM THE SOLID/LIQUID INTERFACE. THE TWO RATE-LIMITING CASES AND AN INTERMEDIATE CASE ARE SHOWN. . . . . . . . . . . . . . . . . . . . . . . . . . 4-62

FIGURE 4-4. ILLUSTRATION OF SPECIES DISSOLUTION WITHIN A POROUS SOLID. DISSOLUTION ACROSS A PORE WALL I S SHOWN, COUPLED WITH TRANSPORT THROUGH THE SOLUTION-FILLED PORE TO THE EXTERNAL SURFACE . . . . . . . . . . . . . . . . . . . 4-64

xpii

ACKNOWLEDGIIUCTS

The authors wish t o acknowledge the many h e l p f u l comnents, cons t ruc t i ve c r i t i c i s m s , and subs tan t ia l con t r i bu t i ons o f t he members of t he Technical Review Panel: Paul Bishop, Un ive rs i t y o f C inc innat i ; Jesse Conner, Chemical Waste Management, Inc.; John Cul l inane, Jr., USAE Waterways Experiment S ta t ion ; M i l e Gi l l iam, Oak Ridge Nat ional Laboratory; Peter Hannak, Union Carbide Chemicals and P las t i cs Company, Inc.; Hans van der Sloot, ECN, t he Netherlands; and T r i sh Erickson and Calton Wiles, U.S. EPA R isk Reduction Engineering Laboratory (RREL). The EPA Work Assignment Manager was Charles Mashni o f RREL.

xviii

a l

a .cc

1 INTRODUCTION

Solidification/stabil ization (S/S) processes are effective in treating a variety of difficult-to-manage waste materials for reuse or disposal. They are flexible enough to accommodate mixtures of contaminants and economical enough to be used for large volumes of waste. applications are incinerator ash, wastewater treatment sludge, and low-level waste from nuclear power plants. S/S has been identified as the Best Demon- strated Available Technology (BOAT) for treating a wide range of Resource Conservation and Recovery Act (RCRA) nonwastewater 1 isted and characteristic wastes. S/S has also been the treatment technology of choice for 26% o f the remedial actions completed at Superfund sites through fiscal year 1992 (U.S. EPA, 1992).

a guide to promote the best future applications o f S / S processes. The standard bulk materials handling and mixing equipment processes used in S/S processes make the technology appear simple. challenges to the successful application of S/S processes. Resources Oocument (TRD) describes S/S process screening procedures and summarizes the status of S/S processes to assist users and reviewers in their selection, planning, and application of S/S technology.

S/S is frequently the technology of choice fo r immobilizing soils and sludges containing one or more metal contaminants. S/S is often chosen also for waste with poor handling quality (e.g., a dense, viscous sludge) or for large volumes of waste that are difficult to treat using other technologies (e.g., power plant desulfurization sludge).

Therefore, selection of the binder requires an understanding of the chemistry of the bulk material, the contaminants, and the binder, as well as of the complex interactions among the various components, to ensure efficient and reliable results. Although there is no sure prescription for selecting a successful binder, a well-structured testing program guided by an understanding o f the mechanisms involved in S/S systems will reduce uncertainty in the selection process.

Some common S/S

This document i s a technical resource for the S/S user community and

However, there are significant This Technical

The morphology and chemistry of S/S-treated waste are complex.

1-1

1.1 BACKGROUND

1.1.1 Definition o f Solidification and Stabilization

The term "solidification/stabil ization" (S/S) refers to a category of waste treatment processes that are being used increasingly to treat a wide variety of wastes-both solid and liquid. designed and used to accomplish one or more of the following objectives:

Generally, S/S processes are

Reduce contaminant/pollutant mobility or solubility

Improve the handling and physical characteristics of the waste by producing a solid with no free liquid

Decrease the exposed surface area across which trans- fer or loss of contaminants may occur.

Numerous other terms, such as "immobilization" and "fixation," have been used to refer to S/S technology. are preferred here because they encompass the variety o f mechanisms that may contribute to contaminant immobilization by this technology. refers to a process in which materials are added to the waste to produce a solid. This may or may not involve a chemical bonding between the toxic contaminant and the additive. "Stabilization" refers to converting a waste to a more chemically stable form. This conversion may include solidification, but it almost always includes use o f a physicochemical reaction to transform the contaminant to a less mobile or less toxic form. processes such as bioremediation are not included in this definition o f S/S (Wiles, 1987).

"Solidification" and "stabilization"

"Solidification"

Note that biological

1.1.2 Position of SIS in the U.S. EPA Environmental Manasement Options Hi erarchr

The U.S. Environmental Protection Agency's (U.S. EPA) hierarchy of hazardous waste management is shown in Figure 1-1. descending order of emphasis, technical alternatives for the management o f

hazardous waste. be instituted to reduce the volume of waste at the source or to recover, reuse, or recycle the waste. destructive treatment methods should then be examined. inants, treatment technologies that destroy the contaminant are preferred.

The hierarchy lists, in

Pollution prevention and waste minimization programs should

If the waste cannot be eliminated or reduced, For degradable contam-

1-2

.

FIGURE 1-1. U.S. ENVIRONMENTAL PROTECTION AGENCY’S HIERARCHY OF HAZARDOUS WASTE MANAGEMENT

1-3

I

However, S/S processes have an important place in the hierarchy because o f their ability to treat otherwise intractable wastes.

1.1.3 ADD^ i cati on o f Sol idi f icationMtabi 1 ization

S/S processes are used to manage numerous types of wastes, such as those covered by Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remediation projects. As shown in Table 1-1, S/S processes have been identified as the Best Demonstrated Available Technology (BDAT) for a variety of Resource Conservation and Recovery Act (RCRA) nonwastewater wastes. such as nuclear, municipal ash, and wastewaters and slurries.

inexpensive and versatile method of treating large amounts of material with a variety o f contaminants.

S/S processes have been applied to a variety of wastes,

In the case o f contaminated soils and debris, S/S is a relatively

For example, a review of 487 Records of Decision (RODS) from the 1980s showed that 53 sites (11%) documented S/S as at least one component of the source control remedy (U.S. EPA, 1989a). In fiscal year (FY) 1988, S/S processes were used at 25% of the active Superfund sites (U.S.

EPA, 1989b). Waste types treated in these projects included soil, sediment, sludges, 1 iquids, and debris. Contaminant types included volatile organic compounds (VOCs) at 21 sites, polychlorinated biphenyls (PCBs) at 19 sites, and inorganics, including metals, asbestos and cyanide, at 43 sites (U.S. EPA, 1989a). It should be noted that more than one type of contaminant may have been present at a given site.

The ROD analysis indicated that, while wastes containing some VOC contamination are treated by S/S processes, the VOCs were not the prime target. treated to immobilize inorganic contaminants (see Section 4.4.3). However, whenever VOCs are present, the possibility o f their release as air emissions during treatment needs to be considered. of VOCs required pretreatment prior to S/S treatment. processes on wastes with VOC contamination, 33 percent reported using pretreatment; of those without VOCs, only 3 percent used pretreatment.

As shown in Table 1-1, S/S processes can be used for a number of types o f sludge that contain inorganic contaminants and, in some cases, inorganics mixed with organics. present, the waste is typically incinerated initially.

Low levels o f VOCs can be incorporated coincidentally in a waste

Sites contaminated with high levels Of the sites using S/S

L

In cases where high levels of organics are S/S processes can be

1-4

TABLE 1-1. RCRA WASTES FOR WHICH SOLIDIFICATION/STABILIZATION IS IDENTIFIED AS BEST DEMONSTRATED AVAILABLE TREATMENT TECHNOLOGY (BDAT)

BDAT Treatment/ Code Waste Description Treatment Train Reference

DO01

DO02

DO03

DO05

0006

DO07

DO08

DO09

DO10

DO1 1

F006

F007

F008

Ignitable (40 CFR 261.21(a) (2) )

Other corrosives (40 CFR 261.22 (a ) (2 ) )

Reactive sulfides (40 CFR 261.23 ( a ) ( 5 ) )

Bari um

Cadmi um

Chromium

Lead

Mercury (subclass)

Sel eni urn

Silver

Some wastewater treatment sludges

Spent cyanide plating bath solutions

P1 at i ng sludges from cyanide processes

S/S (one alternative)

S/S (one a1 ternative)

S / S (one a1 te rn at i ve)


S/S (except batteries)


s/s S/S (t260 mgfkg total Hg)

s/s s/s A1 kal i ne Chlorination t Precipitation + s/s A1 kal ine Chlorination i Precipitation t s/s A1 kal i ne Chlorination t Precipitation + s/s

55 FR 22714

55 FR 22714

55 FR 22714

55 FR 22561

55 FR 22562

55 FR 22563

55 FR 22565

55 FR 22572

55 FR 22574

55 FR 22575

54 FR 26600

54 FR 26600

54 FR 26600

1-5

TABLE 1-1. RCRA WASTES FOR WHICH SOLIOIFICATION/STABILIZATION IS IDENTIFIED AS BEST DEMONSTRATED AVAILABLE TREATMENT TECHNOLOGY (Continued)

BDAT Treatment/ Waste Description Treatment Train Reference Code

FOO9

FOll

F012

FO19

F024

F039

KO01

KO06

Spent stripping and cleaning solutions from cyanide processes

Spent cyanide solutions from salt bath cleaning

Quenching wastewater treatment sludges from cyanide processes

Wastewater treatment sludges from coating of aluminum except for some zi rconi um phosphating processes

Process wastes from the production of certain chlorinated aliphatic hydrocarbons

Leachates from 1 i sted wastes

Bottom sediment sludge from the treatment of wastewaters from wood preserving processes that use creosote and/or pentachlorophenol

Wastewater treatment sludge from the production of chromium oxide green pigments (anhydrous or hydrated)

A1 kal i ne Chlorination + Precipitation + S I S

El ectrol yt i c Oxidation + A1 kal i ne Chlorination + Precipitation + s/s Electrolytic Oxidation + A1 kal i ne Chlorination + Precipitation t s/s s/s

Incineration t S I S

S/S (metals)

Incineration + s/s

S/S (hydrated form only)

54 FR 26600

54 FR 26600

54 FR 26600

55 FR 22580

55 FR 22589

55 FR 22607

54 FR 31153

55 FR 22583

TABLE 1-1. RCRA WASTES FOR WHICH SOLIDIFICATION/STABILIZATION IS IDENTIFIED AS BEST DEMONSTRATED AVAILABLE TREATMENT TECHNOLOGY (Continued)

BDAT Treatment/ Code Waste Description Treatment Train Reference

KO15

KO22

KO28

KO46

KO48

KO49

KO50

KO51

KO52

KO61

Still bottoms from distillation of benzyl chloride

Distil 1 at ion bottom tars from the production of phenol/acetone from cumene

Spent catalyst from t h e hydrochlorinator reactor in the production of l,l,l- trichl oroethane

Wastewater treatment sludges from the manufacturing, formulation, and loading of lead-based initiating compounds

Dissolved air flotation float from the petrol eum ref i n i ng i ndust ry

Slop oil emulsion solids from the petroleum refining industry

Heat exchanger bundle cleaning sludge from the petroleum refining industry

API separator sludge from the petroleum refining industry

Tank bottoms (leaded) from the petroleum refining industry

Emission control dust/sludge from primary steel production in electric furnaces

Incineration + S f S

Incineration + s/s

Incineration + s/s

Reactive - Deactivation Stabilization

Nonreactive - Stabilization

Incineration t s/s

Incineration t S J S

Incineration +' S/S

Incineration + s/s

Incineration t s/s

S/S ( 4 5 % Zn)

55 FR 22535

53 FR 31156

55 FR 22589

55 FR 22593

53 FR 31160 55 FR 22595

53 FR 31160 55 FR 22595

53 FR 31160 55 FR 22595

53 FR 31160 53 FR 22595

53 FR 31160 55 FR 22595

55 FR 22599

1-7


BDAT Treatment/ Code Waste Descr ip t ion Treatment T ra in Reference

KO69

KO83

KO87

K l O O

K115

U051

U144

U145

U146

U204

U205

U214

U215

U216

Emission con t ro l dust /s ludge from secondary 1 ead smel t i ng

D i s t i l 1 a t i on bottoms from a n i l i n e produc t ion

Decanter tank t a r sludge from coking operat ions

Waste leaching so lu t i on from ac id leaching o f emission con t ro l dust / sludge f r o m secondary lead product ion

Heavy ends from the p u r i f i - c a t i o n o f toluenediamine i n the product ion o f to luene- diamine v i a hydrogenation o f d i n i t r o t o l u e n e

Creosote

Lead acetate

Lead phosphate

Lead subacetate

Selenious ac id

Selenium d i s u l f i d e

Thal l ium ( I ) acetate

Thal l ium ( I ) carbonate

Thal l ium ( I ) ch lo r ide

I n c i n e r a t i o n + s/s I n c i n e r a t i o n + s/s P r e c i p i t a t i o n + s/s

I n c i n e r a t i o n + s/s s/s S/S

s/s s/s S/S

S/S o r Thermal Recovery



55 FR 22568

55 FR 22588

53 FR 31169

55 FR 22568

55 FR 26601

55 FR 22582

55 FR 22565

55 FR 22565

55 FR 22565

55 FR 22574

55 FR 22574

55 FR 3891

55 FR 3891

55 FR 3891

1-8

4

,


Code Waste Desc r ip t i on BOAT Treatment1 Treatment T r a i n Reference

U217

PO74

PO99

PO13

P103

P104

PllO

P113

P114

P115

P119

PI20

Tha l l ium ( I ) n i t r a t e

Nickel cyanide

S/S or Thermal Recovery

E l e c t r o l y t i c Oxidat ion + A l k a l i n e Ch lo r ina t i on t

55 FR 3891

55 FR 26600

P r e c i p i t a t i o n + S/S

Argenate (1-) , bis(cyano- C)-potassi um

Barium cyanide

Sel enourea

S i 1 ve r cyan i de

Tet ra e t h y l lead

T h a l l i c ox ide

Tha l l ium ( I ) s e l e n i t e

Tha l l i urn ( I ) s u l f a t e

Amnonium vanadate

Vanadium pentoxide

E l e c t r o l y t i c Ox ida t ion t A1 k a l i n e Ch lo r ina t i on t SIS

S I S (one a1 t e r n a t i v e )

SIS

E l e c t r o l y t i c Ox ida t ion t A1 k a l i ne Ch lo r ina t i on + P r e c i p i t a t i o n + S I S

I n c i n e r a t i o n t S I S


SIS

S / S o r Thermal Rec ove ry

s/s S I S

54 FR 26600

55 FR 22561

55 FR 22574

54 FR 26600

55 FR 22568

55 FR 3888

55 FR 22574

55 FR 3888

55 FR 3888

55 FR 3889

1-9

applied to decrease contaminant mobility in incinerator ash, if necessary. S/S is, in many cases, the only technology that can be applied to a difficult waste form. in situ or after the material is excavated and have been successfully applied in the field to treat waste. S/S processes generally use simple, relatively inexpensive equipment and are cost-competitive with other treatment options. Availability of services from a number of vendors and an established record of field performance help minimize management and regulatory barriers to acceptance of the technology.

ability of the S/S matrix to decrease contaminant mobility by a combination of physical and chemical mechanisms. however, not well understood. Long-term testing is difficult because environmental factors affecting the wastes are not defined. The measurement of long- term environmental exposure is cumbersome at best. Accelerated tests, if available, are not calibrated against real environmental effects. Methods need to be developed for measuring the combined effects o f environmental factors. treated and the commercial secrecy surrounding some of the binder systems available on the market. chemistry involved, it is difficult to predict the long-term performance of a binder/waste combination.

Despite its flexibility and broad appeal, S/S treatment is not appropriate for all wastes. alternative for material containing inorganics, semivolatile and/or nonvolatile organics. technologies for treating wastes containing only volatile organics (see Section 4.4.3). and nonvolatile organics requires a site-specific treatability study or non- site-specific treatability study data generated on waste which is very similar (in terms of type of contaminant, concentration, and waste matrix) to that to be treated. clearly not a meaningful indication of the degree of immobilization for low- solubility organic contaminants. extraction (e.g., the Total Waste Analysis (TWA)) has been recommended.

S/S processes can treat contaminated soil or lagoon sludge either

Laboratory experiments and field experience have demonstrated the

The exact nature of these mechanisms is,

However, the main difficulties are the broad variety of wastes to be

Without an understanding of the mechanisms and

It i s generally appropriate as a treatment

S/S treatment is typically not the preferred choice in

Selection of S/S treatment for waste containing semivolatile

The use of an aqueous leaching methodology such as the TCLP is

Therefore, the use of a nonpolar solvent

However, this recommendation is still under consideration by EPA because it i s

1-10

unclear how the r e s u l t s o f a so lvent e x t r a c t i o n r e l a t e t o t h e environmental m o b i l i t y o f a contaminant i n groundwater. Also, there are few i f any data t h a t demonstrate t h a t the chemical i n t e r a c t i o n between an S/S b inder and an organic contaminant i s s t rong enough t o r e s i s t leach ing by an aggressive nonpolar ex t rac tan t . Therefore, one o f the p o t e n t i a l p i t f a l l s o f us ing S/S technology t o t r e a t waste w i t h s i g n i f i c a n t nonpolar organic contaminants i s the i n a b i l i t y t o adequately assess the ex ten t of contaminant immobi l i za t ion caused by S/S treatment.

A ca re fu l t r e a t a b i l i t y t e s t i n g program, guided by exper t knowledge, i s t y p i c a l l y requ i red t o formulate, t e s t , and apply an S/S t reatment system. The need f o r t r e a t a b i l i t y study da ta and the importance o f conducting appro- p r i a t e l e a c h a b i l i t y t e s t s as p a r t o f t he study, a re mandatory i f organics a re present i n the waste.

1.2 PURPOSE AND SCOPE

1.2.1 Objec t ives

Th is Technical Resources Document (TRD) i s intended t o be a user's guide, emphasizing technology t r a n s f e r and promoting the bes t poss ib le f u t u r e uses o f S/S processes. It addresses t h e f o l l o w i n g questions:

When are S/S processes t h e p re fe r red treatment techno1 ogy?

How do I evaluate a l t e r n a t i v e S / S processes t o s e l e c t t h e c o r r e c t one?

What are the co r rec t and i n c o r r e c t ways o f us ing S/S processes?

How do I design the c o r r e c t process?

The s p e c i f i c d e t a i l s and approach o f each waste treatment p r o j e c t vary, depending on the needs and circumstances o f t h e s p e c i f i c p r o j e c t . It i s no t poss ib le t o p rescr ibe the d e t a i l s o f a s p e c i f i c S / S p r o j e c t because t h e r e are so many var iab les. However, some genera l ized procedures f o r S/S implemen- t a t i o n can be defined. Applying these procedures w i l l enhance u n i f o r m i t y and consistency, thus he lp ing t o overcome d i f f i c u l t i e s sometimes encountered dur ing the app l i ca t i on o f S /S technology. As t h e phrase "Technical Resources Document" impl ies, t h i s document i s a techn ica l resource f o r t h e S/S user comnunity. Technical in fo rmat ion r e l a t i n g t o S/S i s sumnarized throughout t h e

1-11

text. documents to allow the reader access to more detailed background and technical information pertaining to S/S.

studies in Chapter 2. in the selection and optimization of an S/S treatment technology. addresses the following aspects of each phase of an S/S treatability study, starting with the sampling and waste characterization phase and ending with the field demonstration phase:

Where the information is lengthy, references are provided to other

The document provides guidance in conducting S/S treatability High-quality treatability studies are an important step

Chapter 2

Information requirements

Acceptance criteria

Technology screening and testing procedures

Sequence of activities

Decision points

Chapter 3 is a review o f analysis and test methods. Chapter 4 is a compilation of technical resources information on S/S processes, divided into 10 different sections. Chapter 5 is a discussion o f S/S technology shortcomings and limitations. discussion of fruitful areas for further research. Chapter 7 provides biblio- graphic data for the references cited in the text. Appendix A consists of information checklists to provide users with guidance in planning and conduct-

Chapter 6 is a description of ongoing research and a

ing S/S treatability studies. Overall, the TRD gives an appraisal of S/S technology, with a "how-

to" theme for technology screening. provide detailed instructions, because these are project-specific and cannot be prescribed based on generic information. the options for pretreating waste to develop material with particle size distribution and other properties suitable to S/S treatment. selection of the pretreatment approach is site specific.

It does not address design issues or

For example, the TRD describes

However,

1-12

e 1.2.2 Scope

This sec t i on broad ly charac ter izes the categor ies o f wastes and the types o f processes covered i n t h i s document.

1.2.2.1 Waste Types 1

As s ta ted i n Sect ion 1.1, S/S processes have been app l i ed t o a wide v a r i e t y o f wastes, both hazardous and nonhazardous, nuc lear and nonnuclear, inorganic and organic, l i q u i d and s o l i d .

under CERCLA, RCRA, and o ther environmental laws o r acts. CERCLA s o i l s and sludges are emphasized because CERCLA technology screening and performance requirements a re t h e most de ta i led . i s i d e n t i f i e d as BOAT f o r many RCRA wastes (Table 1-1).

on ma te r ia l s covered by environmental regu la t i on , some c lasses of wastes are no t addressed. n o t covered. t o r y Commission (NRC) r a t h e r than the U.S. EPA, are n o t s p e c i f i c a l l y addressed

i n the TRD. However, the l a r g e body o f l i t e r a t u r e on nuc lear S/S technology prov ides an impor tant resource (Kibbey e t al. , 1978), and much o f t he S/S technology developed by the nuc lear comnunity i s app l i cab le t o EPA-regulated wastes. however, S/S technologies may be app l i cab le t o these wastes. l i q u i d rad ioac t i ve and hazardous tank wastes have been s t a b i l i z e d w i t h a cement-based system t h a t s a t i s f i e s EPA’s hazardous waste regu la t i ons and U.S. Department of Energy 1 ong-term performance c r i t e r i a (Peek and Woodrich, 1990).

The pr imary wastes o f i n t e r e s t i n t h i s document a re wastes regu la ted

RCRA i s discussed because S/S treatment

Because the p r i n c i p a l aim o f t h i s document i s t o p rov ide in fo rmat ion

Aqueous wastes contaminated w i th organics and/or meta ls are Nuclear wastes, which are regu la ted by the U.S. Nuclear Regula-

Mixed wastes are not s p e c i f i c a l l y discussed i n t h i s document; For example,

1.2.2.2 Processes

S/S technology inc ludes many c lasses o f i m n o b i l i z a t i o n systems and app l ica t ions ; example classes inc lude inorgan ic b inders o r organic binders, low-temperature processes (e.g., pozzolan ic) o r high-temperature processes (e.g., v i t r i f i c a t i o n ) , i n s i t u app l i ca t i ons o r ex s i t u app l i ca t ions , and S/S

as a so le treatment technology o r as a component o f a treatment t r a i n . scope o f t h i s TRD s p e c i f i c a l l y excludes on ly v i t r i f i c a t i o n and the format ion o f ceramics, which invo lve the a p p l i c a t i o n o f very h igh temperatures

The

1-13

(>1,5OO-'F). V i t r i f i c a t i o n i s discussed i n a separate U.S. EPA guidance document c u r r e n t l y under p repara t ion [b ib l i og raph ic c i t a t i o n needed].

1.2.3 Audience

This document i s intended f o r persons p lanning o r apply ing S/S processes t o hazardous waste management. a b i l i t y t e s t i n g and p r o j e c t p lanning approach lead ing t o se lec t i on o f an e f f e c t i v e S/S technology and g ives techn ica l background on S/S t reatment methods. f o r s e l e c t i o n and design o f S/S treatment methods. technology i s presented i n d e t a i l e d t e x t desc r ip t i ons supported by summary tab les, check l i s t s , and f i g u r e s t o in t roduce users who are u n f a m i l i a r w i th S/S technology t o the key concepts. serve as a ready reference f o r experts.

The document descr ibes t h e t r e a t -

I t i s intended t o p rov ide technology t r a n s f e r t o persons respons ib le In fo rmat ion about S/S

The tab les, check l i s t s , and f i g u r e s a lso

1.2.3.1 CERCLA Appl ica t ions

For CERCLA pro jec ts , t he users o f the TRD may inc lude respons ib le p a r t i e s (RPs), Remedial P ro jec t Managers (RPMs), con t rac tors , and technology vendors. Each has a d i f f e r e n t r o l e i n designing, conducting, and eva lua t ing S/S process t e s t i n g and se lec t i on under CERCLA, as descr ibed below.

Cur ren t ly , RPs p lan and manage c lean up a t approximately h a l f o f t h e Superfund s i t es . execut ing S/S process t e s t i n g and eva lua t ion under federa l o r s t a t e overs ight .

RPMs perform p lanning and overs igh t o f t h e remediation. i n t r e a t a b i l i t y i nves t i ga t i ons depends on the designated l ead o rgan iza t i on ( federa l , s ta te , o r p r i v a t e ) . The i r a c t i v i t i e s genera l l y inc lude scoping the t r e a t a b i l i t y study, es tab l i sh ing the da ta q u a l i t y ob jec t ives , s e l e c t i n g a cont rac tor , i ssu ing a work assignment, overseeing t h e execut ion o f t he study, and in fo rm ing o r i n v o l v i n g the p u b l i c as appropriate.

T r e a t a b i l i t y s tud ies f o r S/S process t e s t i n g and eva lua t ion a re genera l l y performed by remedi a1 con t rac tors o r technology vendors. The i r r o l e s i n t r e a t a b i l i t y i nves t i ga t i ons i nc lude prepar ing work p lans and o the r suppor t ing documents, complying w i t h regu la to ry requirements, execut ing t h e study, analyz ing and i n t e r p r e t i n g the data, and r e p o r t i n g t h e r e s u l t s .

A t enforcement s i tes , RPs are respons ib le f o r p lanning and

The i r r o l e

1-14

The RPs, RPMs, contractors, and vendors participate in identifica- tion of proposed response action, technology screening, development of remedial action alternatives, and evaluation of remedial action alternatives. The TRD provides S/S process-specific information to assist users through the CERCLA planning process.

1.2.3.2 RCRA Applications

Technology screening at RCRA treatment facilities is driven by the regulations, the specific technologies available at the facility, and the permit conditions. immobilization technologies i n place with a menu of permitted treatment options available (U.S . EPA, 1989b). Consequently, screening at a RCRA TSD facility means determining whether each proposed waste is treatable by the available permitted immobil ization technology. treatability is the ability of the treated waste to pass all the required tests for acceptance for disposal, operators and engineers match wastestreams to S/S treatment options, design treatability studies, and select test methods. of characteristically hazardous waste who treat their waste to remove the requirements for Subpart C disposal.

A treatment facility probably has one or more specific

The criterion for satisfactory

The TRD will help RCRA TSD facility

It also will help generators

1.3 REGULATORY CONSIDERATIONS

This section is intended to provide a brief introduction to the major regulatory considerations for S/S. regulations, this discussion does not attempt to be comprehensive, but rather provides an overview of the regulatory framework within which S/S is generally applied. It is very important for anyone considering the use of S/S treatment to consult the regulatory agencies that have authority over that waste. State and local regulations may vary widely, and implementation of regulatory requirements is often developed on a site-specific basis, particularly in the case of Superfund sites.

Due to the complexity of the

1.3.1 Reaulatory Framework

Cleanup and disposal o f hazardous wastes are regulated primarily by two federal laws and their amendments.

1-15

F i r s t i s t h e Resource Conservation and Recovery Ac t o f 1976 (RCRA),

These as amended by the Hazardous and S o l i d Waste Amendments o f 1984 (HSWA). g i v e EPA a u t h o r i t y t o regu la te d isposal o f hazardous waste and se t standards f o r treatment.

Environmental Response Compensation and L i a b i l i t y Act (CERCLA) o f 1980, as amended by the Superfund Amendments and Reauthor izat ion Act (SARA) o f 1986. CERCLA regu la tes the cleanup o f s p i l l e d ma te r ia l s and abandoned hazardous waste s i t e s .

However, CERCLA Sect ion 121(d)(2) requ i res t h a t Superfund response ac t ions comply with o ther environmental laws t h a t are app l i cab le o r re levan t and appropr ia te requirements (ARARs) (U.S. EPA, 1989~) . Determinat ion o f ARARs i s s i t e -spec i f i c . regu la t i ons apply t o t h e Superfund s i t es .

The second major law r e g u l a t i n g hazardous waste i s t h e Comprehensive

Generally, CERCLA s i t e s are no t regu la ted by RCRA d i r e c t l y .

If por t i ons o f RCRA regu la t i ons c o n s t i t u t e ARARs, then these

1.3.2 RCRA Land Disposal R e s t r i c t i o n s

The p a r t o f RCRA t h a t most a f f e c t s the use o f S/S i s t h a t r e l a t e d t o the Land Disposal Res t r i c t i ons (LDRs), a lso r e f e r r e d t o as "landban." The LDRs were inc luded i n RCRA as p a r t o f the Hazardous and S o l i d Waste Amendments (HSWA) o f 1984 f o l l o w i n g a growing concern t h a t hazardous waste being disposed i n the ground (such as i n a l a n d f i l l ) would even tua l l y be re leased i n t o the environment desp i te containment e f f o r t s . Under HSWA, l and d isposa l o f hazardous waste i s p r o h i b i t e d unless i t has been t r e a t e d f i r s t . U.S. EPA i s requ i red t o es tab l i sh treatment standards f o r each type o f RCRA hazardous waste. The RCRA d e f i n i t i o n o f " land disposal," o r "placement," inc ludes b u t i s n o t l i m i t e d to :

any "placement" o f hazardous waste i n a l a n d f i l l , sur face impoundment, waste p i l e , i n j e c t i o n we l l , land treatment f a c i l i t y , s a l t dome formation, s a l t bed formation, underground mine o r cave, and concrete bunker o r vau l t . (RCRA 3004(k))

LDRs apply on ly t o wastes t h a t a re land-disposed a f t e r t he e f f e c t i v e date o f t he r e s t r i c t i o n s . disposed p r i o r t o the da te o f the r e s t r i c t i o n s be removed and t rea ted .

That i s , t he LDRs do n o t r e q u i r e t h a t wastes land-

1-16

However, wastes being treated under CERCLA remedial response actions may still fall under the land disposal restrictions if RCRA regulations apply as ARARs.

treatment standards (U.S. EPA, 1989c), specified in 40 CFR Part 268: As discussed above, U.S. EPA has established three types of LDR

a. A concentration level to be achieved prior to disposal of the waste or treatment residual (the most common type o f treatment standard)

b. A specified technology to be used prior to disposal, or

c. A "no land disposal" designation when the waste i s no longer generated, is totally recycled, is not currently being land disposed, or no residuals are produced from treatment.

Treatment standards are established on the basis of the Best Demon- strated Available Technology (BDAT) rather than on risk-based or health-based standards. duction of toxicity, mobility, or volume of the waste. To be "demonstrated," a treatment technology must be demonstrated to work at a full-scale level, as opposed to bench-scale or pilot-scale. commercially available. S/S has been identified as BDAT for a variety of waste codes. These waste codes are listed in Table 1-1.

concentration levels. concentrations, any technology that can achieve the required concentration- based levels may be used (i.e., the BDAT used by U.S. EPA to set the standards is not the required technology). specific waste code, U.S. EPA selects a subset of the hazardous constituents found in the waste (known as "BDAT constituents") and sets treatment standards for each of these constituents. constituents, only the treatment standards for the "BDAT constituents" must be met before the wastes can be land-disposed. The residues from treatment of an originally listed waste (e.g., ash or scrubber water) are also listed RCRA hazardous wastes (because of the "derived from" rule), and are therefore also prohibited from land disposal unless they meet the treatment standards for the waste code of the original listed waste from which they derive (U.S. EPA,

"Best" is defined as the technology that offers the greatest re-

"Available" means that a technology i s

The majority o f LOR treatment standards promulgated to date specify For wastes with treatment standards expressed as

To establish a concentration level(s) for a

Although the waste may contain additional

1-17

1989d). waters.

t h a t technology must be used t o t r e a t the waste unless an Equiva lent Treatment Method P e t i t i o n i s approved by U.S. EPA. demonstrate t h a t t h e a l t e r n a t i v e technology achieves an equ iva len t measure o f performance.

Sometimes, bo th a concentrat ion standard and a t reatment s tandard apply t o t h e same waste code. usua l l y address d i f f e r e n t contaminants i n t h a t waste. General ly, t he technology-based treatment i s app l ied f i r s t , then t h e waste i s t e s t e d f o r t h e concentrat ion and f u r t h e r treatment i s app l ied i f necessary t o meet t h e concentration-based standard.

U.S. EPA recognized t h a t no t a l l wastes can be t r e a t e d t o t h e LDR treatment standards and t h a t a1 t e r n a t i v e treatment standards and methods o f land d isposal may prov ide s i g n i f i c a n t reduc t ion i n the t o x i c i t y , m o b i l i t y , o r volume o f wastes and may be p r o t e c t i v e o f human hea l th and the environment. The LDRs t h e r e f o r e prov ide the fo l l ow ing compliance op t ions t o meeting t h e r e s t r i c t i o n s discussed above:

Separate standards are es tab l i shed f o r wastewaters and nonwaste-

I f a t reatment standard i s promulgated as a spec i f i ed technology,

To be granted, t h e p e t i t i o n must

When t h i s i s the case, the two standards

T r e a t a b i l i t y Variance: This op t i on i s a v a i l a b l e when U.S. EPA has se t a treatment standard as a concent ra t ion l e v e l , but because a generator’s waste d i f f e r s s i g n i f i c a n t l y from the waste used t o s e t t h e standard, t he promulgated treatment standards cannot be met o r the BDAT technology i s inappropr ia te f o r t h a t waste. (For the purposes o f the LDRs, CERCLA s i t e managers a re considered generators o f hazardous waste.) Under a t r e a t a b i l i t y variance, U.S. EPA approves an a1 t e r n a t i v e treatment standard t h a t must be met before t h a t waste can be land-disposed.

Equiva lent Method P e t i t i o n : Th is op t i on i s a v a i l - ab le when U.S. EPA has se t a treatment standard t h a t s p e c i f i e s a technology (e.g., i nc ine ra t i on ) . Gener- a t o r s may use a d i f f e r e n t technology (e.g., chemical t reatment) i f they can demonstrate t h a t t h i s techno logy w i l l achieve a measure o f performance equiva- l e n t t o t h a t o f t he spec i f i ed technology.

No M i g r a t i o n P e t i t i o n : T h i s op t ion may be used t o meet any o f the f o u r types o f LDR r e s t r i c t i o n . e ra to rs may land-dispose o f wastes t h a t do n o t meet t h e LDR r e s t r i c t i o n i f they can demonstrate t h a t no

Gen-

1-18

hazardous constituents above health-based levels will migrate from the disposal unit or injection zone for as long as the wastes remain hazardous.

Delisting: This option may be used to demonstrate that a waste is nonhazardous and therefore not subject to any o f the RCRA subtitle C hazardous waste regulations, including the LDRs. Delisting only applies when the CERCLA waste is a listed RCRA hazardous waste. Characteristic wastes need not be delisted, but they must be treated to no longer exhibit the characteristic before they can be considered nonhazardous. Generators must demonstrate that (1) the waste does not meet any of the criteria for which the waste was listed as a hazardous waste; and (2) other factors, including additional constituents, do not cause the waste to be hazardous.

1.3.3 ApDlication o f land Disposal Restrictions to CERCLA Sites

CERCLA Section 121(d)(2) specifies that on-site Superfund remedial actions shall attain "other Federal standards requirements, criteria, limitations, or more stringent State requirements that are determined to be legally applicable or relevant and appropriate (ARAR) to the specified circumstances at the site" (U.S. EPA, 1989d). In addition, the National Oil and Hazardous Substances Contingency P1 an (NCP) requires that on-site removal actions attain ARARs to the extent practicable. Off-site removal and remedial actions must comply with legally applicable requirements.

constitute placement of a restricted RCRA hazardous waste. Therefore, the CERCLA site manager must answer these three questions:

For LDRs to be applicable to a CERCLA response, the action must

1. Does the response action constitute placement?

2. Is the CERCLA substance being placed also a RCRA hazardous waste?

3. Is the RCRA waste restricted under the LDRs?

With respect to the first question, if the waste is transported off site and placed i n a land disposal unit as defined by RCRA (landfill, surface impoundments, waste pile, injection well, land treatment facility, salt dome formation, underground mine or cave, concrete bunker, or vault), placement

1-19

occurs. On-site disposal of wastes is often less well defined. U.S. EPA uses the concept of "areas of contamination" (AOCs), which are viewed as the equivalent of RCRA units to determine if LDRs apply. An AOC is delineated by areal extent of contiguous contamination. Such contamination must be continuous, but may contain varying types and concentrations of hazardous substances (for example, a waste source such as a waste pit, landfill, or pile, and the surrounding contaminated soil). For on-site disposal, placement occurs when wastes are moved from one AOC into another. consolidation of wastes from different AOCs into a single AOC, or excavation from an AOC for treatment in a separate unit such as an incinerator or tank that is within the AOC followed by redeposit into the same AOC. Placement does not occur when wastes are left in place o r moved within a single AOC (for example, treatment in situ, capping in place, or processing within the AOC- but not in a separate unit such as a tank-to improve structural stability).

is a RCRA hazardous waste. Site managers are not required to presume that a substance is a RCRA hazardous waste unless there is affirmative evidence to support such a finding. listed wastes (those waste types or compounds specifically listed in 40 CFR Part 261) and characteristic wastes (wastes exhibiting the characteristics of ignitability, corrosivity, reactivity, or toxicity, as defined in 40 CFR Part 261). Infor- mation on the source, prior use, and process type is usually required and can be obtained from facility business records or examination o f processes used at the facility.

may apply:

Examples of placement include

The second question entails determining whether the CERCLA substance

There are two types o f RCRA wastes:

I n addition to the two categories of RCRA wastes, three principles

The "derived from" rule

The "mixture rule"

The "contained in" interpretation

First, the "derived from" rule (40 CFR 2 6 1 . 3 ( ~ ) ( 2 ) ) states that any solid waste derived from the treatment, storage, or disposal of a listed RCRA waste is also a listed waste, regardless of the concentration of hazardous constituents. For example, ash and scrubber water from incineration of a listed waste

1-20

(I

I

are hazardous on t h e bas is o f t h e derived-from ru le . However, wastes der ived from a c h a r a c t e r i s t i c waste are hazardous on ly i f they e x h i b i t t h e character- i s t i c .

t h i s ru le , when any s o l i d waste and a l i s t e d hazardous waste are mixed, t he e n t i r e mix ture i s a l i s t e d hazardous waste. Mix tures o f s o l i d wastes and c h a r a c t e r i s t i c hazardous wastes are hazardous on ly i f t h e m ix tu re e x h i b i t s a cha rac te r i s t i c .

Sol i d Waste Memorandum dated November 13, 1986). any mix tu re o f a nonso l id waste and a RCRA-listed hazardous waste must be managed as a hazardous waste as long as the mater ia l conta ins (i-e., i s above health-based l e v e l s o f ) t h e l i s t e d hazardous waste. For example, i f s o i l o r groundwater conta ins a l i s t e d hazardous waste, t h a t s o i l o r groundwater must be managed as a RCRA hazardous waste as long as i t "conta ins" the waste.

I f a waste i s a RCRA-listed hazardous waste, a "der ived from" waste, o r a mix tu re o f a l i s t e d waste and a s o l i d waste, t he waste must be d e l i s t e d i n order t o be exempted from the RCRA system. be de l i s ted , on ly t rea ted t o no longer e x h i b i t t he c h a r a c t e r i s t i c . t a ined i n " waste a l so does no t have t o be de l i s ted ; i t o n l y has t o no longer "conta in" t he hazardous waste.

I f the answers t o the f i r s t two questions determined t h a t placement w i l l occur and t h a t the waste i s a RCRA hazardous waste, t h e t h i r d s tep i s t o determine a p p l i c a b i l i t y o f the landbans as spec i f i ed by t h e treatment standards promulgated i n 40 CFR P a r t 268. promulgated f o r the waste i n question, the landbans apply and t h e waste must be t rea ted i n accordance w i t h these standards. For severa l o f these standards the BOAT used t o de r i ve the standard i s S/S.

Another p r i n c i p l e i s t he "mixture r u l e " (40 CFR 261.3(a)(2)). Under

The t h i r d p r i n c i p l e i s the "contained in" i n t e r p r e t a t i o n ( O f f i c e o f Under t h i s i n t e r p r e t a t i o n ,

C h a r a c t e r i s t i c wastes need not A "con-

I f treatment standards have been

1.3.4 Toxic Substances Contro l Act

The Toxic Substances Contro l Act (TSCA) regu la tes numerous t o x i c chemicals, many of which are not commonly encountered i n hazardous waste. However, one group o f compounds t h a t i s regulated under T S C A - po l ych lo r i na ted biphenyls (PCBs) - i s a f a i r l y common type of contaminant a t Superfund s i t e s . PCB-containing wastes (o ther than the C a l i f o r n i a L i s t Wastes) - for example, l i q u i d s t h a t conta in both PCBs above 50 ppm and RCRA hazardous wastes -

1-21

genera l l y requ i re cleanup when t h e t o t a l PCB l e v e l s a re g rea te r than 50 ppm. However, 40 CFR 761.120(a)(l) excludes s p i l l s t h a t occurred p r i o r t o May 4,

1987, from the scope o f the U.S. EPA’s PCB S p i l l Po l i cy . The U.S. EPA recognizes t h a t o l d s p i l l s requ i re s i t e -by -s i t e eva lua t ion because o f the l i k e l i h o o d t h a t t he s i t e invo lves more pervasive PCB contamination than f r e s h s p i l l s , and because o l d s p i l l s are genera l l y more d i f f i c u l t t o c lean up than f resh s p i l l s ( p a r t i c u l a r l y on porous surfaces such as concrete). Therefore, s p i l l s t h a t occurred before May 4, 1987, are t o be decontaminated t o requ i re - ments establ ished a t t he d i s c r e t i o n o f t he U.S. EPA, u s u a l l y through i t s reg iona l o f f i c e s .

1.3.5 Other Environmental ReQulations

I n a d d i t i o n t o RCRA, CERCLA and TSCA, o the r environmental l e g i s l a - t i o n may be app l i cab le t o the use o f S/S:

The Clean Water Ac t regu la tes the discharge o f l i qu id

The Clean A i r Act regu la tes t h e re lease o f p o l l u t a n t s

e f f l u e n t s t o waters o f t he U.S.

i n t o t h e a i r .

The Safe Dr ink ing Water Act con t ro l s l e v e l s o f p o l l u t a n t s i n d r i n k i n g water and regu la tes underground i n j e c t i o n we l ls .

The Occupational Safety and Heal th Act regu la tes exposure o f workers t o t o x i c substances and harmful work p rac t i ces .

S ta te and/of l o c a l regu la t i ons p e r t a i n i n g t o hazardous wastes, which may be more s t r i n g e n t than the federa l regu la t ions .

I n t h e event t h a t S/S produces e f f l u e n t s o r cond i t i ons which f a l l

As noted a t t he beginning o f t h i s section, consu l ta t i on w i t h a l l under the j u r i s d i c t i o n o f one o r more o f these acts, compliance would be requi red. cognizant regu la to ry o f f i c i a l s responsib le f o r a p a r t i c u l a r waste or s i t e i s advised before under tak ing treatment.

1-22

e 2 SOLIDIFICATION/STAEILfZATION tS/Q

TECHNOLOGY SCREENING PROCEDURES

2.1 INTRODUCTION

2.1.1 Overview

The process of technology selection, evaluation, and optimization i s frequently referred to as "technology screening." A treatment technology that has been properly screened prior to full-scale implementation has the highest probability of success in the field.

process and the steps needed to select and test an appropriate S/S process for each waste type. Figure 2-1 shows the major steps in the technology screening process and their order of implementation. spond to each of these major steps.

before conducting treatability studies. information requirements for characterizing the waste, including guidance on waste sampling. An example of a Sampling and Analysis Plan is provided in Appendix 6. Section 2.3 addresses the need for, and issues related to, establishing S/S treatability performance objectives or acceptance criteria. Regulatory, technical, and institutional requirements are discussed, and an approach for setting performance criteria is presented. Section 2.4 overviews the generic technology screening process leading to the selection of S/S rather than other types of technologies and references documents offering more detail on this subject.

treatability testing for S/S processes. compatibility screening. waste/binder mixtures, including binder screening and optimization. Sec- tion 2.7 addresses bench-scale performance testing, and Section 2.8 discusses pilot-scale testing. testing becomes more specific to the individual waste form.

(Figure 2-1) are emphasized:

This chapter provides guidance on the S/S technology screening

Sections 2.2 through 2.8 corre-

Sections 2.2 through 2.4 describe activities that must be undertaken Section 2.2 discusses the fundamental

Sections 2.5 through 2.8 describe in detail each o f the tiers of Section 2.5 addresses waste/binder

Section 2.6 discusses laboratory screening of

During each sequential tier o f treatability testing, the

Three points relating to the technology screening process

The screening process often requires several iterations through some or all o f the steps.

2-1

Section 2.2

Section 2.3

Section 2.4

Section 2.5

Section 2.6

Section 2.7

Section 2.8

FIGURE 2-1.

Site Sampling Site Characteristics Analytical/Engineering

Waste Characteristics S/S Solutions? I

Appropriate Waste/Binder

Bench-Scale Performance Testing

Feasibility? e- l Pilot or Field Testing I e- Feasibility?

- uo

Successful Unsuccessful I SOLIDIFICATION/STABILIZATION TECHNOLOGY SCREENING

2-2

A decision point occurs at the end of each step, and, depending on the outcome of the analysis, it may be necessary to return to an earlier stage of the screening process, modify the approach, and repeat one or more steps.

specific circumstances require a flexible approach because not all projects have the same set of needs and resources. Under certain circumstances it may be prudent to skip steps or entire sequences of steps. For example, minimal or even no treatability testing might be required for a well-developed S J S process applied to a simple waste. Project-specific resource limitations may also indicate the need to eliminate certain steps. In designing each treatability study, procedural decisions will have to be made based on the trade-offs of the various alternatives. Eliminating various steps in the technology screening procedure can reduce the 1 i kel i hood of successful technology application; the party respon- sible for the treatability study must evaluate the risk associated with eliminating such steps.

appears not to be feasible (i.e., certain critical performance goals are not being achieved), then it may be advisable to return to an earlier step in the screening process and repeat the screening procedure using a different approach or a different set of assumptions. For example, perhaps a completely different binder type should be tested, or the waste should be pretreated prior to S J S . Unsuccessful S/S treatability studies are not uncomnon, but technical deficiencies can frequently be overcome by testing different binders or by modifying the S/S process.

The screening process must be flexible. Project-

In the event that, during treatability testing, S/S

2.1.2 The Need f o r Treatability Studies

Treatability studies provide valuable site-specific data needed to select and implement the appropriate remedy. The Remedial Investigation/ Feasibility Study (RI/FS) interim final guidance document (U.S. EPA, 1988a) specifies nine evaluation criteria for use in analyzing alternatives. Treatability studies can address seven of these criteria:

Overall protection of human health and the environment

Compliance w i t h applicable or relevant and appropriate requirements (ARARs)

2-3

Implementabi 1 i t y

Reduction o f t o x i c i t y , m o b i l i t y , o r volume

Short-term e f fec t i veness

cos t

Long-term e f fec t i veness

The o ther two c r i t e r i a a f f e c t i n g t h e eva lua t ion and s e l e c t i o n o f t he remedial a l t e r n a t i v e - community and s t a t e acceptance - can in f l uence the dec is ion t o conduct t r e a t a b i l i t y s tud ies on a p a r t i c u l a r technology.

w i t h the proper exper t i se and t r a i n i n g . r i e s , u n i v e r s i t i e s , S/S vendors, o r t r e a t a b i l i t y vendors. EPA (1990a) provides a compi la t ion o f vendors q u a l i f i e d t o per form S/S t r e a t a b i l i t y s tud ies and ind i ca tes t h e types o f media and contaminant groups i n which the f i rms are experienced.

Several documents p rov ide vary ing l e v e l s o f guidance on t h e des ign and conduct o f t r e a t a b i l i t y studies. For example, U.S. EPA (1989e) prov ides gener ic guidance f o r conducting t r e a t a b i l i t y s tud ies under t h e Comprehensive Environmental Response, Compensation, and L i a b i l i t y Act (CERCLA) i n the contex t o f t he RI/FS process and the prepara t ion o f t h e Record o f Decis ion (ROD). discuss ion o f p lanning documentation and da ta q u a l i t y ob jec t i ves . d r a f t document (U.S. EPA, 1990b) provides gener ic t r e a t a b i l i t y s tudy guidance under CERCLA on S/S technology f o r inorgan ic contaminants. Other technology-

T r e a t a b i l i t y s tud ies should be conducted by i n d i v i d u a l s o r groups These may inc lude research labora to-

The guidance, which i s no t s p e c i f i c t o any technology, inc ludes a A r e l a t e d

s p e c i f i c t r e a t a b i l i t y guides have been o r a re i n the process of being pub- l i s h e d f o r s o i l washing, aerobic biodegradation, s o i l vapor ex t rac t i on , chemical dehalogenation, so lvent ex t rac t ion , and thermal desorpt ion. An example o f a f a c i l i t y - s p e c i f i c guidance document i s Bar th and McCandless (1989), which o u t l i n e s S /S t r e a t a b i l i t y t e s t i n g procedures f o r U.S. EPA’s Center H i l l Research F a c i l i t y . A l l o f these documents supplement i n fo rma t ion contained i n t h i s chapter and should be consulted f o r appropr ia te l e v e l s o f guidance.

2-4

2.2 SITE-SPECIFIC BASELINE INFORMATION REQUIREMENTS

The purpose of this section is to discuss the information requfre- ments for technology screening, which are presented in five subsections: Waste Sampling, Waste Acceptance (the acceptability of the waste at the treatability or analytical laboratory in terms of compliance with applicable permits and other requirements), Waste Characterization, Site Characteriza- tion, and Quality Assurancelquality Control (Sections 2.2.1 through 2.2.5). Figure 2-2 presents the sequence of information collection steps. preliminary characterization of the waste is needed to support preliminary decisions about the use of S/S and waste acceptability at the test facility. This information is also used to determine appropriate worker protection provisions for waste sampling. Information for preliminary characterization is usually available from remedial investigation (RI) studies if the waste is from a CERCLA site or from other historical records or testing. studies generally do not provide enough information to determine appropriateness of S/S; therefore, additional waste sampling is required to support a waste-specific determination of the appropriateness of various treatability approaches. project cannot proceed until the problem is resolved. 2-6 briefly outlines guidance on site-specific baseline information needs.

Initially,

The RI

If the waste is not acceptable at the testing facility, the In Section 2.2.6, Table

2.2.1 Waste SamDlinq

The principal objective of waste sampling is to obtain waste samples for analysis and treatability testing that are representative both of the waste as a whole, and of the extremes of waste composition ("hot spots"), which can be used for worst-case testing. ways, as described in Section 2.2.1.1. It is also important to obtain a sufficient number of samples and volume of sample to satisfy the analytical and bench-scale testing requirements, because repeat sampling can be expensive and undesirable.

This can be accomplished in several

2.2.1.1 Composites vs. Hot Spots

Many factors affect site sampling. This document is not intended to provide complete coverage of the many reports that should be referred to for guidance regarding sampling strategies and collection and preservation

2-5

0

Characterization

Section 2.2.1

I I waste Sampling

A

Sedion 2.2.2

Yes1 ,

v Characterize Waste in Detail

Chemical Physical RCRAHazardous Characteristics

Section 2.2.3

FIGURE 2-2. INFORMATION COLLECTION STEPS I N THE TECHNOLOGY-SCREENING PROCESS

2-6

Compile Information on site Characteristics

Section 2.2.4

requirements. Such documents include an EPA soil sampling quality assurance document (U.S. EPA, 1989f), EPA's Solid Waste Test Method Manual, commonly referred to as SW-846 (U.S. EPA, 1986a), Conner (1990, Chapter 17), and U.S. EPA (1989e). A sampling technique developed by U.S. EPA Region 10 especially for S/S treatability studies has been shown to be very effective (U.S. EPA Region 10, 1200 Sixth Avenue, Seattle, UA, (206) 442-5810). The discussion that follows emphasizes several issues applicable to sampling for S/S treatability studies.

Prior to detailed sampling, historical records or a grab sample should be used to determine whether the waste can be sampled safely. The waste material should be surveyed to detemine the necessary sampling apparatus and the procedures that must be used. Also, some analytical data should be available at this point to determine the appropriate level of personal protective equipment.

sampling activity is to obtain waste samples that are representative of the waste as a whole (in terms of both chemical and physical characteristics) and that are collected in sufficient quantity to permit all the necessary analytical tests to be conducted. quantify (U.S. EPA, 1989f). The two approaches to achieving representativeness are as follows:

As indicated in Section 2.2.1, the principal objective o f the

Representativeness i s crucial but difficult to

Combine samples from a wide range of sampling locations both vertically and spatially to produce a single composite sample that represents the "overall average." A variation o f this approach would include compositing the subset of samples with the highest target contaminant levels to produce a "worst-case composite" for bench-scale testing. However, if S/S treatment is applied i n batches, combining samples would not represent high- concentration areas that could occur in a particular batch.

Collect samples from a wide range of locations but do not composite. select the "hot spots" for subsequent bench-scale testing .

Analyze samples individually and

Both approaches have advantages and disadvantages. Compositing samples may be more appropriate when (1) a batch-mixing system i s to be used

2-7

.

i n the f i e l d o r t r e a t e d samples are t o be composited p r i o r t o ana lys i s o r (2) the primary purpose i n conducting the t r e a t a b i l i t y study i s t o compare s t a b i l -

i z a t i o n w i t h some o ther completely d i f f e r e n t treatment process. I n t h e l a t t e r case, t he waste needs t o be uni form t o ensure comparabi l i ty . t h a t are a l ready contained i n ba r re l s a re usua l l y sampled by compositing.

f low-through mix ing system such as a pug m i l l i s employed, o r when t h e process w i l l be app l ied t o i n s i t u waste. the zones o f unusually e levated contaminant o r i n t e r f e r a n t concentrat ions t h a t may cause the process t o f a i l t o s a t i s f y i t s performance c r i t e r i a . o ther hand, the "hot spots" may be d i f f i c u l t t o de f i ne f o r complex waste forms and may lead one i n t h e d i r e c t i o n o f an unnecessari ly expensive S/S process. The issue i s s u f f i c i e n t l y complex t h a t an exper t system would be needed t o s o r t out a l l t he va r iab les and p o i n t t o t h e p re fe r red approach f o r each i n d i v i d u a l case. w i l l be examined by t h e regu la to ry a u t h o r i t y before accept ing t e s t r e s u l t s .

needs o f the waste acceptance, waste charac ter iza t ion , bench-scale screening, and performance t e s t i n g a c t i v i t i e s and should i nc lude a s u i t a b l e q u a n t i t y t o be archived f o r poss ib le l a t e r use. uses 130 kg as the r u l e o f thumb (Barth and McCandless, 1989).

about 110 kg f o r t e s t i n g and an add i t i ona l 20% sa fe ty margin.

t r e a t a b i l i t y study exemption (40 CFR 261.4). l i m i t e d t o a t o t a l o f 1000 kg o f waste i n the f a c i l i t y a t one t ime. fore, the t e s t i n g f a c i l i t y may be r e l u c t a n t t o accept unnecessar i ly l a r g e q u a n t i t i e s o f sample, p a r t i c u l a r l y i f they are performing t r e a t a b i l i t y s tud ies f o r more than one c l i e n t .

One poss ib le s o l u t i o n t h a t a l lows c o l l e c t i o n o f l a r g e r q u a n t i t i e s o f sample i s t o ho ld the sample a t the s i t e and sh ip batches t o t h e t e s t f a c i l i t y as needed. Generally, a t l e a s t 10 kg o f sample i s needed t o p rov ide enough sample t o t e s t ; however, i t i s important t o be s e n s i t i v e t o t h e 1000 kg l i m i t .

I n p rac t ice , sample quan t i t y needs w i l l vary from p r o j e c t t o p ro jec t , depending on the s i ze o f the waste mater ia l , the complexi ty o f waste

Also, wastes

The "hot spot" approach may be more appropr ia te when a continuous

The composite approach r i s k s over look ing

On the

The l o g i c used i n se lec t i ng samples f o r t r e a t a b i l i t y s tud ies

. The amount o f sample c o l l e c t e d should be adequate t o s a t i s f y the

One RCRA-permitted f a c i l i t y t y p i c a l l y Th is inc ludes

Nonpermitted f a c i l i t i e s can perform t r e a t a b i l i t y t e s t s under the However, these f a c i l i t i e s are

There-

2-8

chemistry, QA/QC requirements, and t h e b inder t o be used. Other f a c t o r s a f f e c t i n g sample volume requirements cannot be known beforehand.

2.2.1.2 S t a t i s t i c a l Approaches

I t should be emphasized t h a t sampling i n support o f S/S t rea tab l i t y stud ies encompasses more than the usual s o i l o r waste sampling undertaken i n R I studies a t a Superfund s i t e . quate ly sized and representat ive. l oca t i ons and phys ica l states, each sampling r o u t i n e should be designed t o f i t the waste and t h e s i t u a t i o n . nonhomogeneous mixtures i n s t r a t i f i e d layers o r as poo r l y mixed conglomerates. For such wastes i t i s p a r t i c u l a r l y impor tant t o have a c a r e f u l l y assessed, well-planned, and well-executed sampling r o u t i n e t o ensure t h a t samples are representat ive. s t r a t i f i e d sludges and covered by wastewater, would probably requ i re samples o f the wastewater, t he sludges, and t h e s o i l beneath the sludges. Add i t iona l in fo rmat ion on sampling plans can be found i n t h e ASTM Standard Guide f o r General Planning o f Waste Sampling (ASTM-D-4687-87).

Involvement o f a s t a t i s t i c i a n knowledgeable i n sample des ign can he lp t o minimize cos t by ensur ing t h a t t he samples are c o l l e c t e d i n the most e f f i c i e n t way so as t o p rov ide adequate in fo rmat ion f o r s t a t i s t i c a l ana lys i s o f t h e resu l ts .

It i s impor tant t h a t t h e samples a re ade- Since wastes may be found i n d i ve rse

Wastes t o be t r e a t e d w i t h S/S may occur as

For example, wastes s to red i n sur face impoundments w i t h

Cost i s an impor tant f a c t o r i n determining the ex ten t o f sampling.

Sampling fo r S/S must address fou r areas, depending on t h e s p e c i f i c needs o f t he t r e a t a b i l i t y study and regu la to ry requirements:

Chemical composit ion o f t he unt reated waste

Physical p roper t i es o f t he unt reated waste

Process con t ro l sampling (U.S. EPA, 1990b)

Q u a l i t y assurance/qual i t y cont ro l (QA/QC) representativeness and accuracy

The f i r s t two areas o f sampling apply t o a l l S/S t r e a t a b i l i t y However, sampling f o r process cont ro l app l i es o n l y t o p i l o t - s c a l e studies.

s tud ies and t o the actual S/S remedial operation.

2-9

Assessment of the chemical composition and physical properties of wastes in S/S treatability studies typically is based on a limited number of field measurements. quite complex. measurement uncertainty, field heterogeneities (e.g., in soil and water properties), and sampling variability. from highly variable data, it is crucial that the information upon which the decisions are based be obtained from samples that are selected through the use of statistical sampling design procedures. There are at least three important purposes for statistical sampling design:

However, the variability of field measurements can be This variability i s compounded by several factors such as

In cases where decisions must be made

to ensure that the sampling is representative

to provide numerical estimates for decision making that have quantifiable error limits

to improve sampling efficiency (i .e., to provide estimates that are precise enough at the lowest possible cost)

The design steps for selecting field sampling locations, measurements, and data analyses for S/S treatability studies are similar to those described by other authors for environmental monitoring of chemicals (Keith, 1988; Gilbert, 1987). These five steps can be summarized as follows:

1. Define the sampling zones, sampling frames, and variables(s) of interest.

2. Define a general sample collection strategy for each sampling zone.

3. Develop a statistical model and statistical sampling objectives for each sampling zone.

4. Specify the estimation and/or testing procedures to be employed and their desired statistical properties.

5. Select the sampling design parameters to achieve the desired statistical properties.

The "sampling zone" refers to the specific waste area that must be characterized, typically a contaminated soil body or waste accumulation. The

2-10

"sampling frame" then r e f e r s t o the complete s e t o f p o t e n t i a l sampling u n i t s

(e.g., s o i l grab samples o r core samples) t h a t make up the sampling zone. Each sampling o b j e c t i v e must be r e l a t e d t o a s p e c i f i c v a r i a b l e t h a t can be measured on every sampling u n i t (e.g., waste sample, s o i l sample, water sample). v a r i a b l e and some summary va lue across the e n t i r e sampling zone, such as an average va lue o r a maximum value. General ly, a v a r i e t y o f phys i ca l , chemical, and b i o l o g i c a l p roper t i es (e.g., s o i l moisture, pH, and chemical concentra- t i o n s ) can be measured on each c o l l e c t e d sample.

systematic, random, o r s t r a t i f i e d random, by which sampling l o c a t i o n s w i l l be selected. However, es tab l i sh ing t h e sampling s t ra tegy f o r a p a r t i c u l a r zone descr ibes the f i n a l sampling p lan o n l y i n general terms. To l a y ou t t h e s p e c i f i c sampling p lan i n each zone, the number and loca t i ons o f samples need t o be c l e a r l y de f ined i n terms o f several sampling design parameters. " s t a t i s t i c a l p roper t i es " o f the sampling design, such as es t ima t ion prec is ion , a re then a f u n c t i o n o f these parameters. Examples o f design parameters f o r a mon i to r ing program are as fo l lows: r e p l i c a t i o n s , g r i d conf igura t ion and o r ien ta t i on , sampling times, and measurement p rec is ion . lagoon or waste p i t , the depths a t which samples are taken w i l l be impor tant t o the sample design.

f o r each sampling zone, an appropr ia te mathematical model should be se lected t o descr ibe the an t i c ipa ted s t a t i s t i c a l p roper t i es o f the measured values. It i s impor tant t h a t a knowledgeable s t a t i s t i c i a n be invo lved i n both sample

design and model se lec t ion . The sampling ob jec t i ves f o r each zone can then be re f ined and res ta ted i n terms o f t he var iab les and parameters o f the s t a t i s t i - c a l model. For every sampling ob jec t ive , the est imat ion and in fe rence procedures t o be employed must be s ta ted c l e a r l y and referenced. Generally, these procedures w i l l i nvo l ve e i t h e r es t imat ing o f parameter values f o r t he s t a t i s t i c a l model o r t e s t i n g a s t a t i s t i c a l hypothesis about the parameter values.

Some examples o f mathematical models commonly used i n environmental

I n t h i s way, each ob jec t i ve can be s ta ted i n terms o f t h e measured

The "sampling s t ra tegy" s p e c i f i e s the general method, such as

The

number o f sampling loca t ions , number o f

I f wastes are present i n s t r a t i f i e d l aye rs such as i n a

A f t e r es tab l i sh ing the sampling frame and var iab le (s ) o f i n t e r e s t

assessments and S/S t r e a t a b i l i t y s tud ies are l i s t e d below:

2-11

Gaussian (Normal) Model - used t o est imate t h e average o f some c h a r a c t e r i s t i c of t he waste (e.g., average concentrat ion i n s o i l o f a spec i f i ed contaminant); est imator i s t he a r i t hmet i ca l average o f the measured data.

Lognormal Model - used t o est imate the median o f some c h a r a c t e r i s t i c o f t he waste; t h i s model i s l e s s sens i t i ve t o o u t l i e r data than the Gaussian model; est imator i s the a n t i l o g o f the average o f t h e log- transformed data.

some c h a r a c t e r i s t i c o f the waste (e.g., f r a c t i o n o f t h e waste where the concentrat ion o f a contaminant i s above a spec i f i ed threshold) ; est imator i s a sample propor t ion ca l cu la ted by comparing measured data t o t h e spec i f i ed threshold.

Binomial Model - used t o est imate propor t ions of

Data q u a l i t y ob jec t i ves can then be es tab l i shed a t l e v e l s t h a t make

From a sampling des ign p o i n t o f view, poss ib le r e l i a b l e decision-making about the chemical and phys ica l p r o p e r t i e s o f t he waste from the sampling r e s u l t s . determining the des i red q u a l i t y o f the data amounts t o s e t t i n g requirements f o r t he s t a t i s t i c a l performance o f the se lected es t imat ion and in fe rence procedures. Once the da ta q u a l i t y ob jec t i ves have been determined, t h e s p e c i f i c sampling p lan can be establ ished by s e t t i n g the number o f samples, r e p l i c a t i o n s , e tc . requ i red t o s a t i s f y the data q u a l i t y ob jec t ives .

For example, a data q u a l i t y o b j e c t i v e f o r a p a r t i c u l a r s tudy migt-

be t o assess the waste f o r the average concentrat ion o f a t o x i c metal (e.g., mercury) i n the waste t o w i t h i n an e r r o r o f plus-or-minus 20%.

p roper t i es o f t he mathematical model, t he s t a t i s t i c i a n can e a s i l y determine the minimum number o f samples requ i red t o s a t i s f y t h e da ta q u a l i t y ob jec t i ve . It i s o f t e n use fu l t o have the s t a t i s t i c i a n prepare a t a b l e r e l a t i n g d i f f e r e n t sample s i zes t o t h e corresponding s t a t i s t i c a l confidence leve ls , so t h a t sampling cos ts can be c o n t r o l l e d by t r a d i n g o f f resources a v a i l a b l e aga ins t confidence requi red.

Using t h e

2.2.2 Waste Acceptance

Waste acceptance invo lves analyz ing a representa t ive subsample t o determine compliance w i t h e x i s t i n g f a c i l i t y permi ts f o r t h e l a b o r a t o r y where subsequent a n a l y t i c a l and bench-scale t e s t i n g i s t o occur and t o screen waste f o r the sa fe ty o f f a c i l i t y personnel. The pr imary issue here i s t h a t S/S

2-12

treatment i n the f i e l d usua l l y invo lves c lose contac t between workers and the waste, and there are types of waste t h a t may be too t o x i c t o pe rm i t e i t h e r t h e l abo ra to ry o r f i e l d operat ions t o be conducted sa fe ly . screened from f u r t h e r considerat ion as a candidate f o r S/S t reatment a t t h i s p o i n t . they have a t r e a t a b i l i t y study exemption (40 CFR 261.4 ( f ) (4 ) ) .

chemical analys is before being shipped t o the a n a l y t i c a l o r bench-scale t e s t i n g f a c i l i t y (o r f a c i l i t i e s ) t o meet U.S. Department o f T ranspor ta t ion (DOT) sh ipp ing requirements and t o demonstrate compliance with e x i s t i n g f a c i l i t y permits, permi t exclusions f o r t r e a t a b i l i t y studies, and/or Heal th and Safety Plans. Problematic cons t i t uen ts inc lude d iox ins , furans, rad io - nuc l ides, and excessive l e v e l s o f PCBs o r cyanide. I n add i t ion , t he re may be

app l icab le DOT pre-shipment requirements and hazardous waste mani fest o r d r i v e r c e r t i f i c a t i o n requirements t h a t must be s a t i s f i e d du r ing sh ipp ing. I n add i t ion , even i f t h e waste does not present an unacceptable degree o f hazard a t a permi t ted l abo ra to ry o r t e s t f a c i l i t y , i t may present h e a l t h o r sa fe ty problems f o r workers i n the f i e l d du r ing the f u l l - s c a l e S/S t reatment . The p o t e n t i a l f o r t h i s type o f s i t u a t i o n should a l so be assessed (U.S. EPA, 1990b).

Such wastes are

Less t o x i c ma te r ia l s can be handled by nonpermitted f a c i l i t i e s i f

A representa t ive subsample o f t he unt reated waste must undergo

2.2.3 Waste Charac ter iza t ion

The purpose o f t h i s sec t ion i s t o prov ide a b r i e f overview o f t he var ious waste types and contaminants and t h e i r s u i t a b i l i t y f o r t reatment with S/S technology. I n d u s t r i a l wastes inc lude a wide v a r i e t y o f mater ia ls , both hazardous and nonhazardous. The wastes may come from var ious types of i n d u s t r i e s such as manufacturing, chemical production, petroleum r e f i n e r i e s , o r power production. These wastes t y p i c a l l y inc lude m a t e r i a l s such as sludges, spent c lean ing mater ia ls , p i c k l e 1 iquors, p l a t i n g wastes, and combustion residues. Many o f these wastes are complex mixtures t h a t cannot be categor ized eas i l y . groupings. bu t a re presented t o i l l u s t r a t e the types o f i n d u s t r i a l wastes encountered i n p rac t i ce . s o i l s .

Table 2-1 l i s t s gener ic wastes under broad i n d u s t r i a l These generic waste types are n o t a l l amenable t o S/S t reatment

S/S processes are genera l l y used t o t r e a t sludges o r contaminated Major producers o f hazardous sludge inc lude p r i v a t e i ndus t r i es ,

2-13

TABLE 2-1. GENERAL INDUSTRIAL WASTE CATEGORIES

I ndu s t r y Waste category o r source

Automobi 1 e

Chemical

C hemi cal cl ean i ng Dredging Food processing Leather tanning and f inishing

Metal f inishing and major

Municipal

Nonferrous met a1 s

appl i ance

Paint and painting

Pharmaceutical

P l a s t i c and rubber

Pollution control

Power

Pulp and paper

Refinery and petrochemical

Sanitary 1 andf i l l Steel

Textile

Automobile assembly wastes, foundry plant wastes, neutralized pickle l iquors, t reated plat ing wastes, treatment plant wastes

sludges, treatment plant sludge Acids, a lka l ies , metal-containing

Spent cleaning solutions Contaminated dredge spo i l s Biological treatment sludges Biological treatment sludges, metal-

containing sludges Dissolved metal solutions, pickle

l iquors, r inse water neutralization sludge, treatment plant sludge

Sewage sludges, water treatment sludges

Air pol1,ution control (APC) dust and sludges, lime/limestone wet scrubber sludge, waste pickle l iquors, water treatment sludge

Metal pickling and cleaning wastes, paint sludges

Biological treatment sludge, f i l t e r cake, spent carbon

Biological treatment sludge, metal- containi ng sludge

APC sludges, general spent activated carbon, spent resins, water treatment p lan t sludges

Fly ash, lime/limestone scrubber sludges, boi ler cleaning sol utions

Biological treatment sludges, spent cl ay and f ibe r s

American Petroleum I n s t i t u t e oil/water/ sludge mixtures, biological treatment sludge, spent 1 ime sludges

Landfill leachates APC dust and sludges, metal f ines ,

sca le p i t sludge, waste pickle l iquors, water treatment sludge

Biological treatment sludges, metal-containing s1 udges

Reprinted from: Conner, J . R. 1990. Chemical Fixation and Solidification o f Hazardous Wastes. Van Nostrand Reinhold, New York. p p . 267-268. Used by permission o f Van Nostrand Reinhold.

2-14

u t i 1 i t y companies, and water/wastewater treatment p lan ts . Waste types can be broadly categor ized under a v a r i e t y o f hazardous waste regu la t ions .

2.2.3.1 Regulatory Framework

One major waste type considered i n t h i s document i s wastes covered Hazardous substances under CERCLA are broadly by CERCLA (see Sect ion 1.3.)

de f ined and inc lude a wide v a r i e t y o f mater ia ls . substances" under CERCLA i s de f ined w i t h re ference t o a l l o f t he major federa l environmental s ta tu tes . streams a re designated as "hazardous substances" under CERCLA (40 CFR 302.4) by v i r t u e o f t h e i r regu la t i on under one o r more o f these o ther environmental s ta tu tes . However, petroleum, na tu ra l gas, na tu ra l gas l i q u i d s , l i q u e f i e d na tu ra l gas, and syn the t i c gas usable f o r f u e l a re excluded from the d e f i n i - t i o n o f "hazardous substances" under CERCLA.

Hazardous wastes t h a t are covered by t h e Resource Conservation and Recovery Ac t (RCRA) are de f ined i n the regu la t i ons s p e c i f i e d i n 40 CFR Par t 261. Such wastes are e i t h e r " l i s t e d wastes" o r " c h a r a c t e r i s t i c wastes," as discussed i n the f o l l o w i n g paragraphs (see a l so Sec t ion 1.3).

l i s t e d i n 40 CFR Par t 261 Subpart D. ous waste i d e n t i f i c a t i o n number. Hazardous wastes f rom nonspec i f i c sources

(e.g., spent halogenated so lvents used i n degreasing) a re l i s t e d i n 40 CFR 261.31. Hazardous waste from s p e c i f i c sources (e.g., d i s t i l l a t i o n bottoms from the produc t ion o f acetaldehyde from ethy lene) are l i s t e d i n 40 CFR 261.32. Discarded commercial chemical products, o f f - s p e c i f i c a t i o n mater ia ls , con ta iner residues, and s p i l l res idue (i .e., s p e c i f i c chemicals) a re l i s t e d i n 40 CFR 261.33.

because they have one o r more o f the fou r c h a r a c t e r i s t i c s de f ined i n 40 CFR 261 Subpart C. These hazardous c h a r a c t e r i s t i c s - i g n i t a b i l i t y , c o r r o s i v i t y , r e a c t i v i t y , and t o x i c i t y - are de f ined i n 40 CFR Par t 261 Subpart C.

framework f o r dea l i ng comprehensively w i t h r i s k s posed by the manufacture and use o f chemical substances. Under TSCA, U.S. EPA i s author ized t o regu la te the manufacture, processing, d i s t r i b u t i o n , use, and d isposal o f a chemical o r a mix tu re o f chemicals.

The concept o f "hazardous

Approximately 700 elements, compounds, and waste

"L i s ted wastes" are s p e c i f i c chemicals o r s p e c i f i c types o f wastes Each l i s t e d waste i s assigned a hazard-

Wastes t h a t are n o t s p e c i f i c a l l y l i s t e d may be considered hazardous

The Toxic Substances Control Act (TSCA) prov ides a regu la to ry

The U.S. EPA can p lace r e s t r i c t i o n s on s p e c i f i c

2-15

compounds o r groups o f compounds i f they pose an unreasonable r i s k t o h e a l t h o r t he environment. Po lych lo r ina ted biphenyls (PCBs) are one group o f compounds the U.S. EPA has chosen t o regu la te under TSCA. The d isposal requirements f o r PCBs g iven i n 40 CFR 761.60 apply t o cleanup o f PCB-contaminated wastes o r s o i l s a t CERCLA s i t e s .

2.2.3.2 Contaminant Charac te r i s t i cs and Treatment Types

Contaminant classes i n wastes inc lude meta ls and metal compounds, organics o f var ious types, and o the r cons t i tuents such as anions. The c l a s s o f contaminants i n a waste w i l l i n f luence t h e type o f S/S treatment t h a t can be app l ied t o the waste.

metal anions such as arsenate, molybdate, o r selenate. Metal contaminants cannot be destroyed by chemical o r thermal methods. Therefore, they are e i t h e r ex t rac ted from the waste and concentrated i n t o a more manageable form v i a a s o i l washing/extract ion technology o r a re immobil ized v i a S/S. imnob i l i za t i on i s t h e o r e t i c a l l y poss ib le f o r most metals, t he d i f f i c u l t y and c o s t o f such t reatment va r ies g r e a t l y according t o numerous fac to rs , such as form, speciat ion, quant i t y , and concentrat ion o f t he metal. Some examples o f metals and groups o f metals tes ted f o r S/S t reatment a re l i s t e d i n Table 2-2.

contaminated with organics, a re a l so amenable t o S/S treatment. Th is i s t r u e p a r t i c u l a r l y i f the organics a re present wi th metals o r anions, a re minor components o f t h e waste, o r are nonvo la t i l e and/or viscous (see Table 2-3). Given t h e wide v a r i e t y o f organic compounds, i t i s n o t poss ib le t o prepare a comprehensive l i s t o f organic compounds amenable t o S/S treatment. However, Table 2-4 l i s t s some organic wastes t h a t have been considered as candidates f o r S/S treatment. Solidification/stabilization, e i t h e r d i r e c t l y o r f o l l o w i n g i nc ine ra t i on , has been i d e n t i f i e d as the Best Demonstrated Ava i lab le Technolo- gy (BDAT) f o r some organic wastes (see Table 1-1). However, wastes wi th s i g n i f i c a n t q u a n t i t i e s o f organic mater ia l , p a r t i c u l a r l y v o l a t i l e o rgan ic ma te r ia l , t y p i c a l l y a re t rea ted b e t t e r w i t h o the r types o f treatment technolo-

gy. Organic ma te r ia l s can f requen t l y be ex t rac ted o r destroyed by chemical o r thermal processes. Organics can be d i f f i c u l t t o s t a b i l i z e w i t h inorgan ic S/S b inders and can, i n f a c t , i n t e r f e r e w i t h the s e t t i n g reac t ions (see

Metal and metal compounds inc lude n a t i v e metal, s a l t s o f metals, and

Although

Cer ta in organic-contaminated wastes, such as heavy sludges o r s o i l

2-16

TABLE 2-2. EXAMPLES OF SOME METAL WASTES TESTED FOR SOLIDIFICATION/ STAB1 LIZATION TREATMENT

Contaminant Waste Type Aluminum

Aluminum (and o the r metals)

Antimony (and o ther metals)

Arsenic

Arsenic

Arsenic

Arsenic

Barium

Cadmium (and z inc)

Cadmium (and other metals)

Cadmium (and other metals)

Chromium (and o ther metals)

Chromium (and other metals)

Chromium (and o ther metals)

Chromium (and other m e t a l s )

Copper

Copper

Copper (and z inc)

Copper (and t i n )

Copper (and other metals)

Copper (and other metals)

Lead

Lead (and o the r metals)



Mercury

Nickel (and other metals) Nickel (and other metals)

Metal f i n i s h i n g

Aluminum anodiz ing sludge

B a t t e r y manufacturing f l u e dus t

Phosphoric ac id f i l t e r cake

F l y ash

Herb ic ide waste

Phosphoric ac id f i l t e r cake

Various

S a l t s l u r r y

Bat tery p l a n t sludge

Contaminated s o i l

Chromium p l a t i n g sludge

Aluminum anodiz ing sludge

Chromic ac id r i n s e


Cata lys t

Cata lyst subs t ra te

F i l t e r press cake

Foundry sand

M e t a l f i n i s h

C1 a r i f i e r sludge

Por t land cement k i l n dust

Bat tery p l ant sludge

Bat tery manufacturing f l u e dust


Chlor-a1 ka l i mercury c e l l

Bat tery p l a n t sludge

Metal f i n i s h i n g sludge

2-17

TABLE 2-2. EXAMPLES OF SOME METAL WASTES TESTED FOR SOLIDIFICATION/ STABILIZATION TREATMENT (Continued)

Contaminant Waste Type

Nickel (and metals)

S i 1 ver

Sodi um

T i n (and metals)

Zinc (and cadmium)

Zinc (and copper)

Zinc (and copper)

Zinc (and metals)

Zinc (and metals)

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals

Mixed metals


Various Metal f i n i s h i n g s a l t sludge

Ba t te ry manufacturing f l u e dus t

M e t a l s a l t s l u r r y

C1 a r i f i e r sludge

F i l t e r press cake

B a t t e r y p l a n t sludge


Pa in t sludge

Foundry sludge

Ore processing leach ing res idue

P r i n t i n g wastewater t reatment sludge

P r i n t i n g wastewater t reatment f i l t e r cake

a Pain t waste i n c i n e r a t o r ash

Electrochemical machining waste

Biosludge from chemical process waste t reatment

C l a r i f i e r sludge

Lagoon sludge

Wastewater t reatment f i l t e r cake

Neut ra l i zed acids

Foundry and baghouse dus t

Note: Sources: Conner, 1990, pp. 269-271; and U.S. EPA, 19899.

Degree o f sol i d i f i c a t i o n / s t a b i l i z a t i o n achieved was n o t reported.

a 2-18

e

a

a

TABLE 2-3. EXAMPLES OF SOME METAL AND ORGANIC MIXED WASTES TESTED FOR SOLlDIFICATION/STABILIZATION TREATMENT

Contaminant Waste Type

Aluminum, pa ra f f i ns , and water

Barium and organics

Chromium and organics

Chromium and organics

O i l , cadmium, chrome, and lead

O i l , lead, chromium, and arsenic

O i l , lead, PCB, and arsenic

PAH and organics

PCB and VOC

Meta ls and o i l

Metals and o i l

Metals, o i l , and s u l f u r

Metals and organics

Metals and organics

Meta ls and organics

Metals and organics

Metals and organics

Metals and organics

Meta ls and organics

Metals and organics

Metals and organics

Metals and organics

Metals and organics

Waste l u b r i c a n t

Coke dust

Tannery waste

D r i l l i n g mud

Ref inery sludge

Ref inery s l udge

Contaminated so i l



Spent o i l r e - r e f i n i n g b leach c l a y

Metal f i n i s h i n g bu f f wash

Synthet ic o i l sludge

Weathered o i l waste

Coating manufacture waste sludge

Coating manufacture wastewater treatment s ludge

Wastewater t reatment p l a n t sludge

Hazardous waste l a n d f i l l leachate

L a n d f i l l leachate

Mixed lagoon sludge

P r i n t i n g waste sludge

Solder s t r i p p i n g s o l u t i o n

Wire manufacture v i n y l waste

Tannery 1 agoon b i os1 udge

Note: Sources: Conner, 1990, pp. 269-271; U.S. €PA, 19899.

Degree o f solidification/stabilization achieved was n o t repor ted.

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TABLE 2-4. EXAMPLES OF SOME ORGANIC WASTES TESTED FOR SOLIDI F ICATION/STABI LIZATION TREATMENT

Contaminant Waste type

Carbon t e t r a c h l o r i d e and carbon

Chlor inated hydrocarbons

Creosote

Kepone

Naphthalene compounds

O i l and grease

O i l and grease

O i l and grease

Pest ic ides

PCB

d i s u l f i d e

PCB

S i 1 i cones

Sol vents

S o l vents

Synthe t ic rubber

V iny l c h l o r i d e and ethylene

Organics

Organics

Organ i cs

Organics

Organics

c h l o r i d e

Waste sludge

Petrochemical manufactur ing waste

Waste sludge


Waste sludge


O i l , soap, and grease i n water

O i l sludge

S1 udge

PCB o i l

Contaminated soil

S i l i c o n e waste

Rubber waste

Pa in t waste

Rubber waste

S1 udge

Pa in t wastewater t reatment sludge

Pa i n t waste sludge

Acry l i c lepoxy p a i n t wash

Mixed lagoon sludge

O i l r e f i n i n g caus t i c waste

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TABLE 2-4. EXAMPLES OF SOME ORGANIC WASTES TESTED FOR SOLIDIFICATION/STABILIZATION TREATMENT (Continued)

Con t ami n ant Waste type

Organics Tall oil resin waste

Organics

Organics

Organic phase o f landfill 1 eachate

Lacquer solvent still bottoms

Organics Synthetic resin waste

Organics Tannery waste

Organics Phenolic resin waste

Note: Sources: Conner, 1990, pp. 269-271; U.S. EPA, 19899.

Degree of solidification/stabilization achieved was not reported.

Section 4.4.3 for a detailed discussion of the issues concerning the stabilization of organic contaminants).

solvents, distillation bottoms, and refinery wastes, are candidates for S/S treatment only in specialized applications where solidification is required temporarily for safety i n transportation or storage, or in spill control work. These wastes are normally incinerated if they are hazardous.

Other constituents o f concern in S/S include several additional nonmetal inorganic species. Table 2-5 lists examples of some inorganic species tested for S/S treatment.

On the other hand, fluid oil- and solvent-based wastes, such as used

2.2.3.3 Sampling and Analysis

Waste characterization for S/S treatability studies goes beyond the requirements of the RI and is usually done after the RI has been completed. This characterization phase involves analyzing untreated waste samples for chemical, physical, and hazardous characteristics. The minimum amount of waste characterization for CERCLA sites is screening for substances on the

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TABLE 2-5. EXAMPLES OF OTHER INORGANIC WASTES TESTED FOR SOL I D I F I CAT ION/STABI L I ZATION TREATMENT

Contarni nant Waste type

Acid waste Metal f i n i s h i n g s o l u t i o n

Acid (and metals) S1 udge

Acid waste (and organics) S1 udge

Boron f l u o r i d e

Caust ic waste

Cyanide (and metal s)

F luo r ide (and metals)

F luo r ide (and organics)

Oxalates, s u l f i d e s (and organics)

P i l o t p l a n t waste

Aluminum drawing waste

P l a t i n g sludge

Calcium f l u o r i d e s ludge

Mixed petroleum r e f i n i n g wastes

Spent pu lp ing l i q u o r

~

Note: Sources: Conner, 1990, pp. 269-271; and U.S. EPA, 19899.

Degree o f sol i d i f i c a t i o n / s t a b i l i z a t i o n achieved was n o t reported.

Hazardous Substances L i s t . Actual chemical analys is f o r each o f these compounds may no t be necessary i f s i t e records c l e a r l y show c e r t a i n substances t o be absent. However, some conf i rmat ion analyses may be necessary. The ob jec t i ve i s t o determine w i t h confidence the pr imary t a r g e t contaminants and any waste substrates o r cha rac te r i s t i cs t h a t may i n t e r f e r e s i g n i f i c a n t l y w i t h the S/S process.

Two add i t i ona l ob jec t ives f o r c o l l e c t i n g waste cha rac te r i za t i on data are t h a t such data are usefu l i n se lec t ing the most s u i t a b l e b ind ing agent f o r the waste and i n p r e d i c t i n g the u l t ima te performance of t he waste/binder mix ture. While a t present these ob jec t ives are not always achievable, they underscore the need f o r an accurate and s t a t i s t i c a l l y designed database o f waste c h a r a c t e r i s t i c s in fo rmat ion f o r each waste type being evaluated.

2-22

e The amount of new data that must be generated as part of the S/S

treatability study can frequently be minimized by examining waste and site history and any characterization data that may have been already generated. If data exist and are reliable, they may eliminate or reduce the need for additional testing. At a minimum, background information on waste history will allow the subsequent analytical activities to be more focused, emphasizing target contaminants and problem constituents.

Types of characterization data that may be required for the untreated waste include chemical, physical, or physicochemical (i .e., relating to the form of the contaminant as opposed to its bulk concentration). A number o f frequently used testing methodologies are compiled in Chapter 3, and their applicability to untreated waste is indicated. The reasons for generating characterization data include:

To gather information on substances that interfere

To establish baselines for comparison with chemical

with common S/S processes.

data on the treated waste.

To gather information on U.S. EPA hazard characteristics.

To establish the target contaminants and their physicochemical form.

One of the primary reasons for collecting characterization data is to establish the target contaminants in the waste, in terms of both identity and concentration. At a minimum, the waste should be characterized using a "total waste analysis" or the equivalent, including:

Elemental analysis (metals)

Volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs)

Base, neutral, and acid compounds (BNAs) (see Chapter 3 for methods)

The minimum analysis should also include leaching data to define the soluble portion of the contaminant in the waste, yielding an understanding of

2-23

contaminant p a r t i t i o n i n g i n t h e waste. have some in fo rmat ion on physicochemical form. metals, whose r e a c t i v i t y w i t h var ious b ind ing agents can vary s i g n i f i c a n t l y depending on the species present. be expensive, t h e ana lys is program should be thought ou t c a r e f u l l y . o f m ic rocharac ter iza t ion data inc lude valence s t a t e i n fo rma t ion f o r elements such as arsenic (As) o r chromium ( C r ) , s o l i d phase cha rac te r i za t i on , elemental analys is , and s t r u c t u r a l charac ter iza t ion . Sect ion 3.5 prov ides a b r i e f overview o f procedures f o r mic rocharac ter iza t ion . Deta i led micro- cha rac te r i za t i on i s t y p i c a l l y used o n l y i n research and development p ro jec ts .

Charac ter iza t ion o f wastes from CERCLA s i t e s should inc lude a t l e a s t substances on t h e Hazardous Substances L i s t (both organics and meta ls) . Also, i f n o t c o l l e c t e d as p a r t o f t he basel ine da ta discussed above, data on the so lub le ( leachable) contaminants i n the waste need t o be generated t o estab- l i s h the t a r g e t contaminants whose leachab i l i t i e s must be reduced du r ing t h e S/S process. A l s o needed are data on t h e RCRA hazard c h a r a c t e r i s t i c s o f t h e waste. The f o u r types o f hazard c h a r a c t e r i s t i c s a re t o x i c i t y , i g n i t a b i l i t y ,

r e a c t i v i t y , and c o r r o s i v i t y . I f present, t h e hazard c h a r a c t e r i s t i c s f o r i g n i t a b i l i t y , r e a c t i v i t y , and/or c o r r o s i v i t y may prec lude s t a b i l i z a t i o n o r a t l e a s t i n d i c a t e t h e need f o r pretreatment.

Basel ine da ta can inc lude a v a r i e t y o f parameters and, by d e f i n i - t i on , are needed t o assess how t h e parameters change du r ing S/S treatment. Such da ta may be e i t h e r chemical (e.g., pH, Eh, t o t a l and leachable contaminants) o r phys ica l (e.g., s p e c i f i c g r a v i t y , permeabi l i ty , phys ica l s ta te, t o t a l so l i ds , p a r t i c l e s i ze d i s t r i b u t i o n , presence o f debr is , dustiness,

If possib le , i t i s des i rab le a l so t o This i s t r u e p a r t i c u l a r l y f o r

Because d e t a i l e d mic rocharac ter iza t ion can Examples

a

v i scos i t y , etc.). data t h a t demonstrate the hazardous na ture of t h e waste and thus c o n s t i t u t e the bas is f o r t he S/S treatment. The hazardous c l a s s i f i c a t i o n may be based upon e i t h e r so lub le (e.g., T o x i c i t y C h a r a c t e r i s t i c Leaching Procedure [TCLP]) o r t o t a l (ac id -d iges t i b le ) contaminant concentrat ions. I f t h e waste i s n o t l e g a l l y hazardous and i f there i s no o the r regu la to ry -dr iven need t o s t a b i l i z e the waste, t he re may be no need t o proceed with the S / S pro jec t .

i n t e r f e r e w i t h t h e S/S process. ents, depending on t h e b ind ing agent contemplated.

Perhaps the most impor tant base l ine data a t t h i s stage are

Another cha rac te r i za t i on data category i s cons t i t uen ts t h a t may These inc lude a g rea t v a r i e t y o f cons t i t u -

Examples are o i l and

2-24

grease and so lub le s a l t s such as ha l i de f o r cement-based technologies (see Sect ion 4.3).

t i e s and t e x t u r a l c h a r a c t e r i s t i c s data, because heterogeneous wastes conta in- i n g l a r g e blocks o r boulders may be d i f f i c u l t t o process w i thout pretreatment. Also included i n t h i s category are other parameters t h a t w i l l a i d i n t h e se lec t i on o f the b ind ing agent o r the design o f the S/S process. Examples are p a r t i c l e s i ze and water content.

Along w i t h the chemical data, there i s a need f o r phys ica l proper-

2.2.4 S i t e Charac ter iza t ion

In format ion on s i t e cha rac te r i s t i cs i s an impor tant aspect o f the technology screening process. The fo l l ow ing types o f in fo rmat ion are h i g h l y usefu l :

Base1 i n e in fo rmat ion on the geology, hydrology, weather, etc., may cons t ra in the design o f t he f i e l d t reatment system, in f luence p r o j e c t t iming, and have other e f f e c t s .

S i t e l ayou t and p rox im i t y t o needed resources also a f f e c t engineer ing design and, therefore, p r o j e c t cost.

In format ion on s i t e h i s t o r y may prov ide va luable i n s i g h t about the waste, inc lud ing the types o f chemicals t h a t were used a t t he s i t e and the general l o c a t i o n where they were released or disposed of . Knowledge o f s i t e operat ions can a lso suggest metal spec ia t ion (e.g., presence o f an ion ic forms of metal).

Overa l l s i t e - s p e c i f i c concerns w i t h regard t o a remedial a c t i o n p r o j e c t are geared toward evaluat ing waste containment p o t e n t i a l . s i t e parameters i n t h i s regard inc lude the fo l l ow ing (modif ied from Colonna e t al . , 1990).

Important

Area o f t h e s i t e

Permeabi l i ty o f the area so i l s , both for a rev iew o f leaching c a p a b i l i t i e s and f o r poss ib le l i n e r / c a p mater i a1

Amount and type o f rocks and debr is

2-25

Existing groundwater contaminat ion

Base1 ine information on uncontaminated or upgradient

Groundwater flow regimes

Velocity and direction o f both groundwater and ambient

4 Site drainage

Site meteorology

groundwater

air

0

Proximity to populated areas

Location and sensitivity of receptors

Access routes to and from the site, including any United States Department of Transportation (U.S. DOT) restrictions

Available work area/stockpiling area on the site

Final disposal options and their site-specific

Postremediation use of the site

Sensitive environmental areas within the work site, such as floodplains or marshes

i mpl i cations e

Waste product volume increase and its implications for the capacity of the site to contain final product if on-site disposal is required/preferred

Potential for fugitive dust

Ability to mix the materials adequately on the site

Availability o f the binder materials and additives in the amounts required for the entire site

Most o f the site information needs can be categorized as relating to water table, climate, soil characteristics, site layout, o r logistics (U.S. EPA, 1989b).

expected processing, binder stockpiling, and temporary or final waste disposal. Some kinds of processing require stockpiling of untreated excavated wastes, the processed wastes, and the binder. These materials may have to be

In some cases, the waste site cannot provide sufficient area for the

2-26

covered to reduce exposure to wind and precipitation. volume of the waste product, and this added volume could present difficulties if the S/S product is buried in the original waste site excavation. Solutions to problems posed by limited area must be developed on a site-specific basis. Delivery o f preweighed amounts o f the binder directly to the process site is a possible solution. The binder then can be added directly to the mixing area rather than being stockpiled in bulk containers.

disposal zone in the waste area creates four problems:

Binders increase the

The presence of an elevated water table extending into the potential

1. A water table poses the possibility o f existing groundwater contamination.

2. Excess water (especially flowing water) can cause excavation difficulties.

3. A water table creates the potential need for dewatering a saturated waste material prior to its processing.

e 4. Also, if on-site disposal i s selected, there is a higher potential for leaching of the disposed waste, and there probably will be a requirement for a permanent groundwater monitoring system and collection of leachate.

All four of these problems have significant cost implications and must be resolved before the final technology selection is made (Colonna et al., 1990).

2.2.5 Quality Assurance/Oualitv Control

Quality assurance/qual ity control (QA/QC) is an important aspect o f waste sampling and characterization. The results of the chemical analyses must be valid and statistically significant.

ing and measurement program have a written and approved Quality Assurance Project Plan ( Q A P j P ) . 1979b). The specified QA/QC requirements apply to all environmental data collection, monitoring, and measurement efforts authorized or supported by the U.S. EPA. It is important that .anyone undertaking an S/S treatability study

The U.S. EPA’s quality assurance policy requires that every monitor-

These requirements are specified in Costle (1979a and

2-27

understand U.S. EPA QA/QC objectives and requirements in order to achieve data qual i ty .

measurement errors that may enter the data collection and measurement system at various phases of the project during sampling, sample handling/ preparation, and analysis. The U.S. EPA Superfund Treatability Study Protocol (U .S .

EPA, 1990b) and the documents cited therein provide an overview of U.S. EPA QA/QC guidelines for treatability studies, including a discussion of the following:

Another objective of the QA/QC program is to assess and identify

Data quality objectives (DQO)

Preparation of the Quality Assurance Project Plan (QAPjP)

The need to identify the sources and types o f errors that may occur during the sampling, analysis, and treatabi 1 i ty measurement process

The need for qual ity control samples

Data qual i ty indicators , measurement errors, and documentation

2.2.6 Guidance for Site-Specific Information Requirements

Table 2-6 lists several guidelines pertaining to the sampling and analysis activities that support the S/S technology screening process, as discussed in Section 2.2. For many remedial action projects involving S/S, particularly those involving relatively simple sites, not all of the guidance in Table 2-6 will necessarily apply. be additional issues and concerns not listed in Table 2-6.

F o r large, complex projects, there may

2.3 PERFORMANCE OBJECTIVES

Treatability performance objectives or performance standards are specified values of the properties of S/S-treated wastes as determined by specific tests or measurements. The properties tested are those that are legally mandated and/or considered crucial for predicting the efficacy and long-term reliability o f S / S . defined set of measurable performance objectives.

Every remedial action project needs a clearly The success or failure of

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TABLE 2-6. GUIDANCE FOR COLLECTING BASELINE INFORMATION

1.

2.

3 .

4.

5.

1.

1.

2.

3 .

4.

SamDlina Guidelines

Consistent with agency guidance (see section 2.2.1). Issues such as sampling techniques, sample preservation and storage, holding times, chain-of-custody, etc.

Sampling locations statistically randomized for representativeness.

Samples composited prior to analysis for representativeness.

Debris, large rock fragments, vegetative material, etc., removed, unless they are not to be separated from the waste prior to treatment in the field.

"Hot spot" samples collected for worst-case analysis.

Waste AcceDtance Criteria

Waste complies with transportation and facility (bench-scale treatability testing and/or analytical laboratory) permits as well as with health and safety plans.

Waste Characterization

Total waste analysis for target contaminants.

TCLP and other appropriate leaching data on untreated waste for establishing baseline leaching data and determining the presence of RCRA toxicity characteristic.

RCRA and other hazard characteristic tests as appropriate including the f ol 1 owi ng :

- ignitability - toxicity

- corrosivity - infectivity

- reactivity - (radioactivity)

Other chemical analyses to establish baselines and possible S/S interferences, for example

- PH - oil and grease content

- redox potential

- salt content

- leaching tests

2-29

TABLE 2-6. GUIDANCE FOR COLLECTING BASELINE INFORMATION (Continued)

5. To ta l contaminant analys is a t t he same t ime as a so lub le ( leachable) contaminant analysis, on the same subsample. subsample used t o generate the so lub le data does n o t con ta in a low contaminant l e v e l because o f sample heterogenei ty (avoid f a l s e negat ives) .

This i s t o ensure t h a t t he

6. Basel ine phys ica l c h a r a c t e r i s t i c s o f the unt reated waste:

- physica l s t a t e - dust iness

- p a i n t f i l t e r t e s t and/or - b u l k dens i t y

- s p e c i f i c g r a v i t y - phase separat ion

- permeabi 1 i ty - moisture content

l i q u i d release t e s t

- p a r t i c l e s i z e - p o r o s i t y - h e a l t h hazards

7. Other data on physicochemical form o f the t a r g e t contaminants - X-ray d i f f r a c t i o n , scanning e lec t ron microscopy, o p t i c a l microscopy, valence s ta tes o f redox-sensi t ive contaminants such as As and Cr , organometa l l ics (e.g. , t e t r a e t h y l lead, b u t y l t i n compounds), n icke l -carbonyl , e t c .

8. To ta l waste volume measured o r ca lcu lated.

9. Presence and amount o f debr is t h a t may i n t e r f e r e w i t h S/S.

10. Tex tura l c h a r a c t e r i s t i c s o f the waste:

- o i l y , l i q u i d - c layey

- dry granular - hard massive, e tc .

- sludge

11. Heterogenei ty o f t a r g e t contaminant d i s t r i b u t i o n i n t h e waste.

2-30


1. Suitable QA/QC program, with built-in mechanisms to define data quality objectives, to evaluate sources of error, and to provide suitable documentat ion.

2. Analytical laboratories should possess appropriate qualifications or certifications.

3. Sufficient amount o f analytical replication to permit a statistical analysis of the results (e.g., confidence intervals to address sample heterogeneity).

4. Use of a second analytical laboratory for interlaboratory verification on a portion of the more critical analytical measurements.

Baseline Site Characteristics

1. Fundamental site characterization data:

- geology

- hydrology, surface water and groundwater

- geochemistry, soils

- climatology, meteorology (especially temperature, wind, and rainfall)

2.

3. Compatibility of site with heavy field equipment, for example

Knowledge of the proportion of waste that occurs above the groundwater table.

- topography, slope, presence of obstacles

- ability to excavate

- available space

- storage areas

- characteristics consistent with any special requirements such as dikes, berms, and groundwater diversion or suppression systems

- surface water drainage, etc.

2-3 1


4 . Proximity of site to necessary resources, for example

- water - equipment rentals

- supplies - access routes

- chemicals - disposal facility

- electricity - waste to be tested

5. Proximity of site to possible receptors, for items such as

- noise - volatiles

- fugitive dust - odors

6. Proximity of site to sensitive environmental areas, for example

- floodplains - protected species breeding

- wetlands grounds

- populated areas

7. Measurement of baseline contaminant levels in various media (air, water, soil, etc.) to determine if contaminants were released during the field demonstration.

8. Availability of backfill, if necessary.

the project depends to a large degree upon the ability to satisfy these objectives.

Performance objectives are a function of the compliance requirements selected for the site, the test methods used to evaluate the performance of the stabilized waste, and the analytical procedures (models) used to relate test data to performance objectives (Barich and Mason, 1992). The performance objectives are established early in the process of planning the treatability study. Specifying performance objectives goes hand-in-hand with selecting the

for specific a: if

tests to conduct because the objectives are expressed as result tests. The performance objectives constitute acceptance criter treatment by S/S cannot meet these criteria at the bench scale,

2-32

S/S alone

probably cannot provide s u f f i c i e n t t reatment t o meet s i t e cleanup goals. Once

t e s t methods and performance ob jec t ives are determined, the c r i t e r i a t o be used i n i n t e r p r e t i n g t e s t r e s u l t s can be der ived r e a d i l y (U.S. EPA. 1990b).

Before s p e c i f i c t r e a t a b i l i t y performance ob jec t i ves a re set, t h e data q u a l i t y needs o f t he p r o j e c t must be de f ined (Section 2 .2 .5 ) . The e a r l y implementation o f an appropr ia te QA/QC program and the establ ishment o f DQOs w i l l ensure t h a t data o f known and documented q u a l i t y are generated. For a d e t a i l e d d iscuss ion o f DQOs, see U.S. EPA (1987a). Guidance on OQOs i n t h e

t r e a t a b i l i t y study process can be obtained i n U.S. EPA (1989e). T r e a t a b i l i t y performance ob jec t ives can be grouped i n t o two general

types. app l i cab le o r re levant and appropr ia te requirements (ARARs) f o r t h e s i t e . o ther performance ob jec t i ves may be c l a s s i f i e d as t e c h n i c a l / i n s t i t u t i o n a l (Section 2.3.2). f o r which e x p l i c i t regu la to ry standards do n o t e x i s t . e f fect iveness, a requirement f o r t he S/S-treated waste t o support veh icu la r t r a f f i c , and res is tance o f t h e t rea ted waste t o biodegradation. 1989e, Chapter 3 , prov ides add i t i ona l guidance.

Regulatory performance ob jec t i ves (Sect ion 2.3.1) a re those based on A l l

These r e l a t e t o the c h a r a c t e r i s t i c s o f t he S/S-treated waste Examples i nc lude cos t

U.S. EPA,

2.3.1 peau la to rv Reauiremnts

The regu la to ry requirements p e r t i n e n t t o t r e a t a b i l i t y t e s t i n g o f S/S are those standards t h a t t he remedial a l t e r n a t i v e w i l l have t o meet when implemented a t f u l l scale. The regu la to ry framework f o r RCRA wastes i s c l e a r l y de f ined i n the regu la t ions . The CERCLA regu la to ry framework i s der ived from s i t e - s p e c i f i c ARARs about which general guidance i s g iven below. An ARAR search needs t o be conducted e a r l y on i n the conduct o f t he f e a s i b i l i - t y s tudy and we l l before the onset o f t he t r e a t a b i l i t y tes t ing . ARARs can be numerous, and a process has been establ ished by the U.S. EPA t o i d e n t i f y ARARs f o r Superfund p ro jec ts (Sect ion 121, Superfund Amendments and Reauthor iza t ion Act [SARA] of 1986, Pub l ic Law 99-499). The var ious ARARs o f t e n have d i f f e r - ent goals. d i f f i c u l t t o comply w i t h a l l the goals.

M u l t i p l e goals make i t inc reas ing l y expensive and inc reas ing l y

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e 2.3.1.1 CERCU

There are several types o f ARARs under CERCLA: act ion-speci f ic , chemi cal-speci f i c , and 1 ocation-speci f i c . Act ion-speci f i c ARARs are technology- o r a c t i v i t y - s p e c i f i c requirements o r l i m i t a t i o n s r e l a t e d t o var ious a c t i v i t i e s . Chemical-speci f ic ARARs a re u s u a l l y numerical values t h a t es tab l i sh the amount o r concentrat ion o f a chemical t h a t may be i n o r d i s - charged t o the ambient environment. r e s t r i c t i o n s placed on the concentrat ions of hazardous substances o r t h e conduct o f a c t i v i t i e s s o l e l y because they occur i n a specia l l oca t i on .

De ta i l ed guidance on the ARAR search i s g iven i n U.S. EPA (1988b). Some aspects of ARAR i d e n t i f i c a t i o n t h a t apply t o S/S t r e a t a b i l i t y standards are discussed here.

Most federal laws t h a t con ta in l oca t i on -spec i f i c ARARs are i n s t i t u - t i o n a l o r admin i s t ra t i ve i n nature. These laws regu la te the types o f a c t i v i - t i e s t h a t may take place i n p a r t i c u l a r types of l oca t i ons such as seismic f a u l t zones, f loodpla ins, o r c r i t i c a l h a b i t a t s f o r endangered species, S ta te and l o c a l regu la t ions are more l i k e l y t o p rov ide l oca t i on -spec i f i c ARARs f o r t r e a t a b i l i t y t es t i ng . nondegradation standards f o r p a r t i c u l a r water bodies and basin-wide a i r q u a l i t y standards (U.S. EPA, 1990b, Chapter 3 ) .

A t present, t he re are f e w e x p l i c i t performance standards f o r S/S-treated wastes. The U.S. Nuclear Regulatory Commission (NRC) has es tab l i shed performance standards f o r s t a b i l i z e d nuclear wastes (both h igh- level and low- level ) , but these are no t appl icable t o nonnuclear mater ia ls . Hazardous wastes t h a t are disposed o f on land may be regulated under RCRA, and standards f o r t reatment o f such wastes are c u r r e n t l y being promulgated. Wastes t h a t are s t a b i l i z e d by i n s i t u techniques, such as deep mixing, may no t f a l l under the purview o f RCRA ru les. Wastes t h a t are excavated, t rea ted , and land-disposed o f e i t h e r on o r o f f t he s i t e (i.e., they undergo "placement") may be regu la ted by RCRA r u l e s . f i n e d compressive s t rength of 50 p s i (U.S. EPA, 1986b), b u t the actual t a r g e t value f o r a spec i f i c s i t e may be h igher o r lower depending on s i t e - s p e c i f i c requirements. I n addi t ion, techno1 ogy- and ac t i on -spec i f i c t reatment standards f o r a number of RCRA waste c lasses are named i n the RCRA l and disposal r e s t r i c t i o n s (LDRs)

Locat ion-spec i f i c requirements a re

Per t inent regu la t i ons would inc lude discharge l i m i t s o r

Relevant technology (ac t i on ) -spec i f i c ARARs must be i d e n t i f i e d .

Land-disposed RCRA wastes usua l l y need t o demonstrate a minimum uncon-

2-34

For many waste classes, i nc lud ing inorgan ics and some organic contaminants, treatment standards are expressed as percent reduc t ion i n contaminant leaching, as measured by pre- and post-treatment TCLP t e s t s . Note, however, t h a t there has been a tendency i n RODS t o express t reatment standards, even f o r metal contaminants, i n terms o f reduc t i on o f t o t a l contaminant l eve l s . Th i s poses compl icat ions f o r t h e a p p l i c a t i o n o f S/S technology because, under normal circumstances, S/S n e i t h e r dest roys nor removes t h e contaminant, bu t ins tead immobil izes it. These standards a re d i r e c t l y app l i cab le t o l abo ra to ry screening and bench-scale t e s t i n g o f these waste classes; they can be used t o gauge the e f f i c i e n c y o f S / S treatment du r ing t r e a t a b i l i t y s tud ies. For many organic contaminants, RCRA t reatment standards are expressed as destruction-removal e f f i c i e n c y (DRE), where t h e e f f i c i e n c y o f t he treatment technology i s measured by pre- and post-treatment t o t a l (as opposed t o so lub le) contaminant concentrat ions. (U.S. EPA, 1990b, Chapter 3). by d i l u t i o n o f waste due t o b inder add i t i on . Reduced contaminant concentra- t i o n i n leachate may not r e f l e c t reduced m o b i l i t y o f t h e contaminant unless r e s u l t s have been cor rec ted f o r d i l u t i o n e f f e c t s .

A t many CERCLA s i t e s , t h e ma te r ia l s r e q u i r i n g t reatment cannot be assigned t o s p e c i f i c RCRA waste classes. o f t e n the ma te r ia l s o f concern. performance standard can be der ived by the procedure used t o e s t a b l i s h a t r e a t a b i l i t y var iance under RCRA (U.S. EPA, 1989b). The U.S. EPA has se t t a r g e t cleanup ranges f o r wastes contaminated by the p r i n c i p a l classes o f organic and inorgan ic contaminants (Table 2-7). For an organic Contaminant, t he appropr ia te t r e a t a b i l i t y performance ob jec t i ve i s determined as fo l lows: I f t he t o t a l concentrat ion f o r the contaminant i n the unt reated waste f a l l s below the " th resho ld concentrat ion," then the t o t a l concentrat ion o f t he contaminant i n the S/S-treated waste must f a l l w i t h i n the "concentrat ion range." th resho ld value, then the d i f f e r e n c e between t h e t o t a l concentrat ions o f t he contaminant i n the t rea ted and unt reated wastes must f a l l w i t h i n the "percent reduc t ion range." The relevance o f these gu ide l ines when treatment i s by S/S i s unclear, however, because S / S n e i t h e r destroys nor removes the contaminant, bu t instead imnob i l i zes i t . The same l o g i c appl ies f o r m e t a l l i c Contaminants, bu t the c r i t e r i a a re based on the contaminant concentrat ion i n the TCLP

Resul ts of TCLP t e s t s on post-treatment samples may be in f luenced

Contaminated s o i l and debr is a re For such s i t es , an appropr ia te regu la to ry

I f the o r i g i n a l t o t a l concent ra t ion o f t he contaminant exceeds t h e

2-35

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leachate, r a t h e r than the t o t a l contaminant concent ra t ion (U.S. EPA, 1990b, Chapter 3) .

F i n a l l y , an ARAR search may i d e n t i f y chemical -speci f ic ARARs t h a t should be evaluated du r ing t r e a t a b i l i t y t e s t i n g . Numerical standards t h a t may be ARARs have been promulgated under several federa l laws. These inc lude the Clean Water Ac t (water q u a l i t y c r i t e r i a for p r o t e c t i o n o f human hea l th and ambient water q u a l i t y c r i t e r i a ) , t he Safe Dr ink ing Water Act (maximum contaminant l e v e l s [MCLs] and MCL goals), and RCRA. I f t h e S/S-treated wastes may be disposed o f o f f - s i t e , then the TCLP t e s t and the RCRA c h a r a c t e r i s t i c t e s t s should be spec i f ied ; t h e i r acceptance c r i t e r i a w i l l c o n s t i t u t e one s e t o f performance ob jec t ives . Chemical-specif ic a i r q u a l i t y standards may a l s o apply and t h e ARARs cannot be exceeded. Because ma te r ia l s processing and the p o t e n t i a l f o r v o l a t i l i z a t i o n are much d i f f e r e n t between bench- and fu l l - sca le , a i r q u a l i t y standards are u n l i k e l y t o form the bas is f o r q u a n t i t a t i v e bench- sca le t e s t s (U.S. EPA, 1990b, Chapter 3 ) .

For most S/S pro jec ts , resource l i m i t a t i o n s d i c t a t e t h a t t he t r e a t a b i l i t y t e s t i n g program be r e s t r i c t e d t o a subset o f t he contaminants present on t h e s i t e . according t o the f o l l o w i n g c h a r a c t e r i s t i c s (U.S. EPA, 1990b, Chapter 3):

The contaminants t o be evaluated should be se lected

T o x i c i t y o r ca rc inogen ic i t y - s e l e c t t he m s t harmful contaminants.

M o b i l i t y - se lec t t h e most so lub le contaminants.

Geochemistry - s e l e c t a representa t ive contaminant f rom each o f t h e major f unc t i ona l types present.

Concentrat ion - a l l f a c t o r s be ing equal, s e l e c t t h e contaminants present a t the h ighes t concentrat ions.

Generally, i f the number o f contaminants be ing evaluated i n t r e a t a b i l i t y t e s t i n g exceeds f o u r o r f i v e a t any one t ime, i t becomes inc reas ing l y d i f f i - c u l t t o s a t i s f y the performance ob jec t i ves f o r a l l o f the contaminants. the ROD has been signed and s i t e cleanup goa ls have been spec i f ied , t h e contaminants named the re in should be monitored throughout the t r e a t a b i l i t y study. are summarized i n Table 2-8.

I f

Examples o f regu la to ry performance ob jec t ives f o r CERCLA S/S s tud ies

2-39

TABLE 2-8. EXAMPLES OF REGULATORY ARARs

1.

2.

3 .

4

5.

6.

7.

8.

9.

Total contaminant treatment standards for disposal

Soluble contaminant treatment standards for disposal

a. routine leaching procedure (e.g., TCLP)/ b. other leaching procedure (e.g., ANSI/ANS/IC.I)

Mobility criteria from geochemical transport model

Land activity restrictions (e.g., in seismic fault zones, floodplains, critical habitats o f endangered species)

"Placement" restrictions (e.g., 50 psi unconfined compressive strength criterion)

Air emissions standards

Noise restrictions

Compliance with the Clean Water Act or Safe Drinking Water Act

Compliance with state and local regulations and laws.

2.3.1.2 RCRA

The factors for accepting stabilized waste at a treatment, storage, and disposal (TSD) facility under RCRA are much less complex than for CERCLA. The principal criteria (U.S. EPA, 1989b) are as follows:

~

Paint Filter Test (PFT) for free liquid

Adherence to TCLP maximum concentration limits (see Table 2-9)

~

Screens for hazardous waste characteristics

- ignitability - corrosivity - reactivity - radioactivity Compliance with LDRs (see Section 1.3 for a discussion of the nature and applicability of RCRA Land Disposal Restrictions).

I 2-40

I

TABLE 2-9. TOXICITY CHARACTERISTIC CONSTITUENTS AND REGULATORY LEVELS

EPA HW No.' Constituent (mg/L)

Regulatory Level

DO04 Arsenic 5.0 DO05 Bari urn 100.0

DO18 Benzene 0.5 DO06 Cadmium 1.0

DO19 Carbon tetrachloride 0.5

DO20 Chlordane 0.03

DO21 Chlorobenzene 100.0

DO22 Chloroform 6.0 DO07 Chromium 5.0

0023 o-Cresol 200. Ob

DO24 m-Cresol 200. Ob

DO25 p-Cresol 200.Ob

DO26 Cresol 200. Ob

DO16 2,4-0 10.0

0027 1,4-Dichlorobenzene 7.5 DO28 1,2-Dichloroethane 0.5 DO29 1,l-Di chl oroethyl ene 0.7 DO30 2,4-Dinitrotoluene 0.13'

DO12 Endrin 0.02

003 1 Heptachlor (and its 0.008 hydroxide)

DO32 Hexachl orobenzene 0.13' DO33 Hexachl oro-l,3-butadiene 0.5

DO34 Hexachloroethane 3.0

DO08 Lead 5.0 DO13 Lindane 0.4

2-41

TABLE 2-9. TOXICITY CHARACTERISTIC CONSTITUENTS AND REGULATORY LEVELS (Continued)

EPA HW No.' Const i tuent (mg/L)

Regulatory Level'

0009

DO14

DO35

DO36

DO37

DO38

DO10

DO1 1

Mercury

Methoxychlor

Methyl e t h y l ketone

Nitrobenzene

Pentachlorophenol

Pyr id ine

Sel eni urn

S i l v e r

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10.0

200.0

2.0

100.0

5.0'

1.0

5.0

DO39 Te t rac h l oroethy l ene 0.7

0015 Toxaphene 0.5

DO40 Tr ich lo roe thy lene 0.5

DO4 1 2,4,5-Tri chl orophenol 400.0

DO42 2,4,6-Trichl orophenol 2.0

DO17 2,4,5-TP ( S i 1 vex) 1.0

DO43 V iny l ch lo r i de 0.2

Hazardous waste number

I f 0 - , m-, and p-cresol concentrat ions cannot be d i f f e r e n t i a t e d , the t o t a l cresol (0026) concentrat ion i s used. The regu la to ry l e v e l f o r t o t a l c reso l i s 200 mg/L.

Q u a n t i t a t i o n l i m i t i s greater than the ca l cu la ted regu la to ry l e v e l . q u a n t i t a t i o n l i m i t there fore becomes the regu la to ry l e v e l .

The

2-42

2.3.2 Technical and I n s t i t u t i o n a l Reauirements

I n a d d i t i o n t o regu la to ry requirements, o ther fac to rs may shape the t r e a t a b i l i t y performance ob jec t ives . Technical / i n s t i t u t i o n a l ob jec t i ves are developed from cons t ra in t s imposed by admin i s t ra t i ve fac to rs , by t h e s i t e i t s e l f , o r by t h e waste t o be t rea ted . problems t h a t may d e t r a c t from the imp lementab i l i t y o f t h e S/S process o r from the long-term performance o f S/S-treated waste a t t he s i t e . remediation, developing such ob jec t i ves and so l v ing these problems may be as impor tant as meeting app l icab le regu la to ry requirements.

ou ts ide o f t he regu la to ry domain. For some ob jec t ives , such as cos t -e f fec- t i veness and c o n t r o l l i n g the product ion o f hazardous vapors, q u a n t i t a t i v e acceptance c r i t e r i a may not e x i s t . performance standards f o r p a r t i c u l a r s i t e cond i t ions can be developed.

Some o f the performance ob jec t i ves l i s t e d i n Table 2-10 f o r S/S- t r e a t e d wastes have been stud ied i n depth. Tests f o r these p roper t i es a re w ide ly performed and have been app l ied success fu l l y i n eva lua t ing S/S-treated wastes. Examples o f such p roper t i es are waste volume increase, s u l f a t e o r s u l f i d e content, and l e a c h a b i l i t y , as measured by var ious t e s t s (see Chap- t e r 3 ) . The importance of o ther p roper t i es i n ma in ta in ing the i n t e g r i t y o f S/S-treated wastes i s n o t we l l understood. The corresponding t e s t s may be considered research t e s t s and t h e i r r e s u l t s sub jec t t o var ious i n t e r p r e t a t i o n s (U.S. EPA, 1990b, Chapter 3 ) .

These ob jec t i ves address spec ia l

For successful

Table 2-10 1 i s t s p o t e n t i a l types o f performance ob jec t i ves t h a t f a l l

For many nonregulatory tests , q u a n t i t a t i v e

2.3.3. ADproach f o r S e t t i n q Performance C r i t e r i a

The labo ra to ry t e s t s t o be performed and performance c r i t e r i a f o r these t e s t s t o meet a re chosen a t the same t ime. One should n o t begin the t e s t i n g program w i thou t a c l e a r d e f i n i t i o n o f what r e s u l t s w i l l c o n s t i t u t e success and f a i l u r e . The a v a i l a b l e phys ica l , leaching, chemical, b io log i ca l , and mic rocharac ter iza t ion t e s t s and t h e i r t y p i c a l app l i ca t i ons are discussed i n Chapter 3.

leaching, unconfined compressive s t rength, and f r e e l i q u i d s . These t e s t s a re l i k e l y t o form a t l e a s t a p o r t i o n o f the bas is f o r any regu la to ry eva lua t ion o f the S/S-treated waste.

Every bench-scale t r e a t a b i l i t y s tudy should consider t e s t s o f

2-43

TABLE 2-10. EXAMPLES OF TREATABILITY PERFORMANCE OBJECTIVES BASED ON NONREGULATORY FACTORS'

Object i ve Poten t ia l gener ic t e s t ( s )

O u a l i t a t i v e Object ives

Demonstrate bas ic f e a s i b i l i t y

Reagent cos ts no t t o exceed a

Assay f o r o f f -gass ing o f v o l a t i l e

given amount

compounds

Ensure thorough mix ing

I d e n t i f y s o i l con ta in ing i n t e r f e r i n g minera ls

Treat a minimum propor t i on o f contaminated ma te r ia l on s i t e

guant i t a t i v e Ob iec t ives

Prevent unfavorable reac t ions between waste and b inder

Create a pumpable mix

Ensure complete microencapsulat ion

Volume increase n o t t o exceed a

o f contaminants

th resho ld value

Leaching t e s t One o r more phys ica l t e s t s

Optimize mix; c a l c u l a t e b inder cost per volume s t a b i l i z e d

Measure temperature o f f resh mix tu re

Moni tor a i r w i t h organic vapor detector wh i l e mix ing

Microscopy; v i sua1 examination o f f rac tu red mono1 i t h s

Observation o f b inder m i s c i b i l i t y , we t t i ng dur ing mix ing

X-ray d i f f r a c t i o n

Assay s i t e f o r debr is and l a r g e p a r t i c l e s ; determine handl ing needs

Po ten t i a l r e a c t i v i t y o f aggregates

Pe trograph i c exami n a t i on o f aggregates f o r concrete

L iqu id waste consistency/ c l a s s i f i c a t i o n (see Table 3-3)

Col lec t , analyze any b leed

Calcu late volume change from

w a t e r

treated, unt reated waste bu lk dens i t i es

e

e

2-44

e

TABLE 2-10. EXAMPLES OF TREATABILITY PERFORMANCE OBJECTIVES BASED ON NONREGULATORY FACTORS (Continued)

Ob jec t ive Po ten t i a l gener ic tes t ( s )

Ensure s u f f i c i e n t long-term s t r u c t u r a l i n t e g r i t y

Determine a b i l i t y o f S/S-treated waste t o support heavy equipment soon a f t e r placement

monol i th t o support veh icu la r t r a f f i c

Determine a b i l i t y o f cured S/S

Assure res is tance t o s u l f a t e

Prevent f r a c t u r i n g o f S/S monol i th

a t t a c k on S / S monol i th

C u r t a i l f u g i t i v e dust emissions dur ing f u l l - s c a l e f i x a t i o n

Minimize contaminant leaching

Determine long-term leach behavior

Minimize leachate t o x i c i t y

Resis t b iodegradat ion o f organic contaminants o r aspha l t i c b inders

Reduce contaminant load o r concentrat ion a t t h e receptor t o below th resho ld value

Compressive s t rength Resistance t o we t ld ry and

freeze/thaw s t ress ing

Trace development o f bear ing capaci ty w i t h cone penetrometer

F lexura l s t rength t e s t C a l i f o r n i a bear ing r a t i o Proctor compaction o f subbase

(and s t a b i l i z e d mater ia l , i f i t i s a f r i a b l e soil-cement)

SO, content o f waste

Shr ink/swel l p o t e n t i a l o f subbase mater ia l

P a r t i c l e s i ze ana lys is Moisture content o f wastes

Leaching t e s t s

Acid n e u t r a l i z a t i o n capac i ty Resistance t o redox change Chemistry o f surrounding s o i l

Accelerated aging/weathering and groundwater

t e s t s

Aquat ic bioassays

Biodegradat ion t e s t s

leaching t e s t s Permeabi l i ty Transport modeling

e a U.S. EPA, 1990b

2-45

The currently accepted version of the TCLP leaching test is usually required. However, depending on the anticipated disposal s e t t i ng and environmental or human health risks, TCLP may n o t be adequate and additional leaching t e s t s may be needed. The types of contaminants and t he i r level of hazard and concentration, the planned disposal or reuse scenario, and the S/S approach used a l l influence the selection of leaching t e s t s . Additional leaching t e s t s are par t icular ly important i f there is a need t o characterize the fundamental mechanisms involved (e.g., for r i sk analysis t o receptor populations).

i n i t i a l l y projected on the basis o f s i t e hydrologic conditions. driving force for leachate production ex i s t s , additional leach tes t ing should be considered. transport using a modeling approach. Additional background and guidance on t h i s issue i s provided in U.S. EPA (1989e, Section 3.3). force may n o t exis t . the S/S-treated waste be placed above the seasonal high-water t ab le and an impervious cap and runon/runoff controls be constructed. leaching and physical integri ty t e s t s will usually suff ice t o demonstrate whether the S/S process can be considered re l iab le for the s i t e . by engineering controls o r na tura l processes i s not usually considered in t h i s case (U.S. EPA, 1989e, Chapter 3).

applied performance c r i t e r i a . based on s i te-specif ic factors such as those l i s t e d in Tables 2-8 and 2-10. Selection of tes t ing depends on waste character is t ics , disposal o r reuse scenario, type o f S/S progress, and s c i en t i f i c objectives of the program.

Beyond these basic regulatory requirements, fur ther tes t ing i s I f an aqueous

In addition, i t may be necessary t o evaluate contaminant

An aqueous driving For example, the f inal remedial design may specify t h a t

In such cases,

Attenuation

Strength and freedom from f ree l iquids are two other frequently Other types of measurements should be planned

2.4 INITIAL TECHNOLOGY SCREENIN6

After the performance objectives for a t r e a t a b i l i t y project have been ident i f ied, i t is necessary t o determine what treatment technology or technologies have t h e potential of complying w i t h those performance objec- t ives . This section br ie f ly discusses the screening process whereby S/S i s compared with other treatment a l ternat ives and the most appropriate technology or technologies are selected for fur ther evaluation t o determine compliance with the performance objectives. technology screening process, including " feas ib i l i t y study" (FS) for remedial

Various terms have been applied to t h i s

2-46

a

I.

ac t ions and "economic eva lua t ion /cos t ana lys is " (EE/CA) f o r removal act ions. The screening process i s described i n o ther pub l i ca t ions , such as U.S. EPA (1988c), and i t i s beyond t h e scope o f t h i s TRD t o descr ibe the process i n d e t a i l . Therefore, an overview o f t h e bas ic elements o f t h e process i s g iven i n Section 2.4.1 and r u l e s o f thumb f o r screening problemat ic waste types f o r S/S technology are provided i n Section 2.4.2.

2.4.1 Technoloav Screenina/Feasi b i l i t v Studv Process

I n the broadest sense, t he m a j o r i t y o f wastes a re p o t e n t i a l l y t r e a t a b l e w i t h S/S. Pretreatment can be used t o t rans form an un t rea tab le waste form t o a form t h a t can be t rea ted with S/S. wastes, t he pret reatment requirements may make the technology imprac t i ca l based on cos t o r o ther c r i t e r i a , and there c l e a r l y are s i t u a t i o n s where a d i f f e r e n t type o f technology w i l l be more e f f e c t i v e o r appropr ia te.

However, f o r c e r t a i n

2.4.1.1 CERCLA Techno1 ogy Screening

The f i r s t s tep i n the technology screening process i s t o i d e n t i f y candidate remedial a1 te rna t i ves (treatment/removal technologies o r t reatment t r a i n s ) . A number o f d i f f e r e n t technologies have been developed. Many technologies are app l i cab le on ly t o c e r t a i n types o f wastes. U.S. EPA (1988~) l i s t s the fo l l ow ing broad categor ies o f t reatment technolo- g ies:

For example,

F lu id i zed bed i n c i n e r a t i o n

Rotary k i l n i nc ine ra t i on

I n f r a r e d thermal treatment

Wet a i r ox ida t i on

Py ro l ys i s - i nc ine ra t i on

V i t r i f i c a t i o n ( i n s i t u , ex s i t u )

Chemical e x t r a c t i o n

Glyco la te dech lo r ina t

Sol i d i f i c a t i o n / s t a b i l

on

za t i on

2-47

Chemical reduc t ion /ox ida t ion

Biodegradation

I n s i t u b iodegradat ion

Treatment technologies c o n t i n u a l l y are be ing developed, mod i f ied and re f ined. I n se lec t i ng a remedial a l t e r n a t i v e (which inc ludes s e l e c t i n g the treatment technologies), an ana lys is i s performed w i t h respect t o a number o f d i f f e r e n t eva lua t ion c r i t e r i a . The process described i n t h e Nat ional Contin- gency Plan e n t a i l s a d e t a i l e d ana lys is o f each remedial a l t e r n a t i v e w i t h respect t o n ine d i f f e r e n t eva lua t ion c r i t e r i a i n t h r e e main categor ies. c r i t e r i a are presented below. t rade-o f fs among t h e Primary Balancing C r i t e r i a and must, a t a minimum, a t t a i n the Threshold C r i t e r i a . p u b l i c comment per iod .

These A l l se lected remedies should p rov ide the bes t

The Modi fy ing C r i t e r i a a re evaluated f o l l o w i n g t h e

Threshold C r i t e r i a :

Overa l l Protect iveness o f Human Heal th and t h e Environment. p r o t e c t i o n t h a t t he remedy provides w h i l e desc r ib ing how r i s k s a re e l iminated, reduced, o r c o n t r o l l e d through treatment, engineering cont ro ls , and/or i n s t i t u t i o n a l con t ro l s .

Reauirements. Th is c r i t e r i o n addresses whether a remedy would meet a l l o f t he ARARs o f federa l and s t a t e environmental s ta tu tes and/or p rov ide grounds f o r invok ing a waiver.

Th is c r i t e r i o n evaluates t h e adequacy o f

Comol iance w i t h ADD^ i c a b l e o r Relevant and Aooroor iate

Primary Balancing C r i t e r i a :

Reduction o f T o x i c i t y . M o b i l i t y . o r Volume Throuah Treatment. t reatment performance o f t h e remedy.

Short-Term Ef fect iveness. Th is c r i t e r i o n r e f e r s t o the speed w i t h which the remedy achieves p ro tec t i on , as we l l as the remedy’s p o t e n t i a l t o c rea te adverse impacts on human hea l th and the environment du r ing t h e remedial ac t ion .

This c r i t e r i o n addresses t h e a n t i c i p a t e d

Lona-Term Ef fec t i veness and Permanence. This c r i t e r i o n evaluates the magnitude o f res idua l r i s k and

2-48

t h e a b i l i t y o f t h e remedy t o ma in ta in r e l i a b l e p r o t e c t i o n o f human hea l th and t h e environment over t i m e once the remedial ac t i on has been completed.

techn ica l and admin i s t ra t i ve f e a s i b i l i t y o f execut ing a remedy, i nc lud ing t h e a v a i l a b i l i t y o f ma te r ia l s and serv ices needed t o implement the chosen so lut ion.

ImDlementabi l i tv . This c r i t e r i o n examines the

Cost. This c r i t e r i o n inc ludes the c a p i t a l and opera t ion and maintenance cos ts o f t he remedy.

Modi fy ing C r i t e r i a :

S ta te AcceDtance. This c r i t e r i o n i nd i ca tes whether, based on i t s rev iew o f t h e planned remedial a l t e r n a t i v e , t he s t a t e concurs w i th , opposes, o r has no comment on the pre fer red a l t e r n a t i v e .

Communitv AcceDtance. This c r i t e r i o n evaluates the r e a c t i o n o f t he p u b l i c t o the remedial a l t e r n a t i v e s and t o the U.S. EPA’s Proposed Plan.

A s i m i l a r approach i s employed us ing EPA’s Engineering Evalua- t ion/Cost Ana lys is (EE/CA) f o r se lec t i ng CERCLA removal actions/approaches. I n t h i s case, t h e technology screening takes p lace i n two stages, as shown i h F igure 2-3. F i r s t , a l l a l t e r n a t i v e remedial ac t ions are compared based on t ime l iness and e f fec t i veness t o p ro tec t human hea l th and the environment. Then, the smal ler subset o f remedial ac t ions t h a t s a t i s f y these c r i t e r i a are evaluated based on (a) techn ica l f e a s i b i l i t y , (b) cost, and (c) admin i s t ra t i ve and managerial f e a s i b i l i t y . The process may be i t e r a t i v e and may have several d i f f e r e n t poss ib le outcomes, which are discussed f u r t h e r i n Sect ion 2.4.3.

t i o n o f the remedial act ion l technology i n terms o f t he h ie rarchy o f hazardous waste management (Section 1.1.2). Remedial ac t i ons t h a t a l l ow recyc l i ng , reuse, or recovery o f t h e waste o r some p o r t i o n o f t h e waste are p re fe rab le t o t r e a t - ment and d isposal . For example, a l l o the r fac to rs being equal, smel t ing o r s o i l washing would be pre ferab le t o S/S f o r wastes conta in ing approp r ia te l y h igh metal contents because some contaminants would be recovered and could then be recyc led. when making t h e comparison. res idua ls generated, such as l i q u i d waste produced dur ing s o i l washing.

Another f a c t o r considered du r ing technology screening i s t he posi-

However, i t i s impor tant t o consider t h e f u l l system e f f e c t s One example i s t h e need f o r pret reatment and the

2-49

FIGURE 2-3. GENERAL TECHNOLOGY SCREENING PROCEDURE

2-50

a

No

d e

2.4.1.2 Technology Screening at RCRA TSD Facilities

Remediation under CERCLA and RCRA corrective action are driven primarily by regulations, waste characteristics, and site characteristics and have the full range of available treatment technologies as options. trast, RCRA treatment, storage and disposal (TSD) facilities are driven by the regulations and by the specific permitted technologies available at the facility. Any one treatment facility probably has one or more specific immobilization technologies in place with a limited menu of pretreatment options available (U.S. EPA, 1989b).

treatment technologies to process waste streams while complying with permit conditions. process modifications.

treated waste to pass all the required tests for disposal. determining the potential suitability of S/S for waste treatment at a RCRA TSD facility is provided in Figure 2-4. potentially suitable for S/S, the approach for bench-scale screening is as outlined in Figure 2-5. the tiered approach for S/S treatability testing described in Sections 2.5 through 2.7.

In con-

The RCRA TSD facility personnel need to select, screen, and test

Some flexibility may be gained by using pretreatment options or

The criterion for satisfactory treatability is the ability of the A flowchart for

Once the waste has been found to be

This approach is basically a simplified version of

2.4.2 General Criteria for Not k i n a S/S

Because the applicability o f S/S processes to site-specific wastes depends on several variables, specifying criteria for not using S/S is difficult or impossible without site-specific data. However, it is possible to generalize about criteria that indicate potential S/S inapplicability. Table 2-11 summarizes the types of waste that are generally not amenable to S/S processes or that could pose problems.

2.4.3 Outcome of Technolow Screening

The outcome of the technology screening process is a determination of one of the following (Figure 2-3):

Waste can be treated with S/S without pretreatment.

2-51

FIGURE 2-4. DETERMINING WHETHER S/S IS APPLICABLE AT A RCRA TSD FACILITY (from U.S. EPA, 1989b)

2-52

QQ, Retreatment

I" I

FIGURE 2-5. S/S DECISION TREE AT A RCRA TSO FACILITY (from U.S. EPA, 1989b)

2-53

TABLE 2-11. APPLICABILITY OF SOLIDIFICATION/STABILIZATION TO SITE-SPECIFIC WASTE

1.

2 .

3 .

4 .

5.

6 .

7.

1.

2.

3..

4.

5.

A. WASTES THAT ARE UNSUITABLE FOR S/S'

Wastes tha t a re readily t rea tab le by recycling, reuse, o r recovery technology, a l l other factors being equal.

Wastes t h a t a re t rea tab le using a destructive technology, a l l other fac tors being equal.

Wastes tha t contain 1 and-banned constituents (unless land disposal can be avoided) and other high-hazard materials (e.g., dioxins, high leve ls of PCBs, pest ic ides , etc.).

Waste for which the ARARs cannot be sa t i s f i ed w i t h exis t ing S/S technology (unless AR4Rs are modified).

Wastes tha t have unacceptable physical charac te r i s t ics such as being too so l id o r viscous to mix or handle.

Wastes where waste volume expansion would exceed reuse space constraints.

Wastes tha t a r e t rea tab le using a much l e s s expensive technology, a l l other fac tors being equal.

6. WASTES THAT POSE COMPLICATIONS FOR S/S

Wastes w i t h vo la t i l e organics (pretreatment i s usually required).

Wastes tha t contain a large number of d i f fe ren t types of contaminants.

Wastes t h a t are s i tuated such t h a t f i e ld S/S will be d i f f i c u l t o r expose local receptors t o unacceptable r i sk .

Wastes w i t h large amounts o f interfering/incompatible const i tuents (pretreatment necessary).

Wastes tha t contain organics as the primary contaminants. - a S/S i s not recommended fo r these wastes unless no other option ex i s t s .

I

2-54 ,

Waste can be treated with S/S with pretreatment or coupled with a different technology (treatment train).

Waste can be treated with some type of technology

No treatment technology i s currently available for the

other than S/S.

waste.

I

Wastes that can be treated "as is" with S / S are those whose target contaminants are expected to respond favorably to S/S using at least one known binding agent. with the S/S process.

Wastes requiring pretreatment include materi a1 s that are hazardous by virtue of ignitabil ity, corrosivity, reactivity, infectiousness, presence of radionuclides, or some other property that would normally preclude secure land burial. Such wastes cannot be solidified or stabilized and disposed of in landfills without adequate pretreatment. Wastes that present specific problems, such as excessive escape of volatile organics of concern during treatment, may also fall into this category and require either pretreatment to reduce the volatiles or the use of additives in the S/S treatment formulation to inhibit emissions during S/S processing. pretreat a waste prior to S/S would be to remove an interference with the S/S technology. Conversely, S/S may itself also be the pretreatment step, for example, to improve material handling characteristics prior to treatment by a different technology.

include highly hazardous materials (because S/S does not convert metals or break organics down into basic chemicals), wastes containing excessive interferants that will not respond to treatment, and mixed wastes with complex chemistries that require several pretreatment steps prior to S J S . Such wastes become too expensive to process when compared with the cost for transportation and secure land burial in a RCW-permitted facility. In many cases, these types o f wastes will be treatable using a different type of technology. rare cases, the waste will simply be untreatable. If allowed within regulations such as landban, the waste may be disposed of. If the disposal option is foreclosed, additional research will be needed.

Such wastes should not have properties that would interfere

Another example o f a reason to

Finally, wastes for which S/S is currently not a practical option

In

2-55

2.5 WASTE/BINDER COMPATIBILITY LITERATURE SCREENING

After it has been determined that S/S is a potentially applicable technology for a specific waste (Section 2.4), surveying the technical literature to identify applicable binder types is a good starting point for the treatability study. tion of two to four candidate binders for further evaluation at the laboratory bench-scale screening tier (Section 2.6).

screening step, as outlined in U.S . EPA (1989e). Technical information resources, including information from reports, guidance documents, vendor information, and electronic databases, are useful reference materials, Any available performance and cost information should also be obtained for all binders being considered. bility literature screening processes, as well as the organization of this section, is presented in Figure 2-6. to identify, as simply and as inexpensively as possible, those binder types most suited for the site-specific waste and its contaminants and for the related waste disposal scenario.

The literature screening should result in the selec-

The 1 iterature-screening step basically conforms to the remedy

A flowchart illustrating the waste/binder cornpati-

The objective of this screening step is

2.5.1 Identify Available Binders

The selection of two to four binders for further evaluation is not a requirement, but is recommended because it improves the probability of a successful treatability study and requires minimal additional time and cost. This literature screening step is also intended to minimize potentially expensive trial-and-error bench-scale testing in the laboratory.

scale testing, then the literature screening step is no longer relevant. However, if that binder system proves to be ineffective in bench-scale screening (Section 2.6), then it will be necessary to select and test additional binder systems before it can be concluded that S/S is an inappropriate treatment technology.

If a single binder or binder system has been preselected for bench-

2.5.2 Screenina Process

The principal criteria for waste/binder compatibility literature screening are to determine (a) interferences and chemical incompatibilities,

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Section 2.5.1

Section 2.5.2

I Identify Available I Types of Binders

Screen Binders Based on Literature Information

Interference With Binders Waste Chemistry Considerations Disposal/Reuse cost Process Implementation History

Select 2 to 4 Binders for Bench-Scale Screening Testing

FIGURE 2-6. WASTE/BINDER COMPATIBILITY LITERATURE SCREENING

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.

(b) metal chemist ry considerations, (c) c o m p a t i b i l i t y w i t h the d isposal o r reuse environment, (d) cost , and (e) process t r a c k record. system should be developed t o p rov ide systematic eva lua t ion o f these issues. However, a f u l l y usable system f o r complex waste forms has y e t t o be developed.

I d e a l l y , an exper t

The l i t e r a t u r e screening c r i t e r i a are sumnarized below.

2.5.2.1 In te r fe rences and Chemical Incompatibil i t ies

Proper S/S t reatment us ing pozzolanic b inders may be i n h i b i t e d i n t h e presence o f c e r t a i n chemical const i tuents , such as h igh concentrat ions o f o i l , grease, and o the r organics, as we l l as ch lo r ides and o the r so lub le s a l t s . Cer ta in S/S processes w i l l n o t f unc t i on proper ly i f the chemical environment i s n o t adequately con t ro l l ed . w i t h acids, which not on l y impa i r S/S bu t a lso may r e s u l t i n t h e re lease o f t o x i c hydrogen s u l f i d e gas. b i l i t i e s a re summarized i n Sect ion 4.3 and i n re ferences c i t e d the re in . Ma te r ia l Sa fe ty Data Sheets (MSDSs) f o r i n d i v i d u a l waste components p rov ide another p o t e n t i a l l y use fu l source o f data on in te r fe rences and chemical i n c o m p a t i b i l i t i e s .

For example, sodium s u l f i d e i s incompat ib le

These and o ther types o f waste/binder incompati-

2.5.2.2 Heta l Chemistry Considerations

Metal chemistry i s complex and has no t been examined i n any system- a t i c manner as i t per ta ins t o S/S treatment and t h e chemical mechanisms o f immobi l i za t ion o f contaminated s o i l s . Sect ion 4.2.2 and U.S. EPA (1990b, Appendix 0) summarize some o f the re levan t chemical reac t ions . b ind ing agents such as cement, pozzolan ic binders, o r so lub le s i l i c a t e s are used, the format ion o f metal hydroxides, oxides, and poss ib l y s i l i c a t e s w i l l be an impor tant S/S mechanism. i nso lub le s u l f i d e s a l t s may form w i t h numerous metals. I n add i t ion , metal carbonates, phosphates, and su l fa tes occasional ly can be impor tant i n some systems.

h igh pH (see Sect ion 4 . 1 . 1 ) t h a t are favorable f o r t he immobi l i za t ion o f c e r t a i n meta ls (e.g., N i and Zn) a c t u a l l y may be de t r imenta l t o others. example, As and C r form so lub le an ion ic species a t h igh pH. s o l u b i l i t y o f many metal hydroxides i s a f fec ted by t h e i r amphoteric behavior

When a l k a l i n e

When sodium s u l f i d e i s used, extremely

Numerous chemical complex i t ies e x i s t . Chemical condi t ions, such as

For Also, t h e

2-58

( s o l u b i l i t y increases a t bo th h igh and low pH). The minimum s o l u b i l i t y f o r one metal may be several pH u n i t s d i f f e r e n t from the minimum s o l u b i l i t y f o r another. Geochemical equ i l i b r i um modeling may be necessary t o reso lve issues r e l a t e d t o complex waste chemistr ies.

2.5.2.3 Organic Ched s t r y Considerations for Target Contaminants

I f organic contaminants a re present, t h e b inder se lec t i on must a lso be based upon c o m p a t i b i l i t y with the organic contaminants. discusses some o f t h e types o f b inders and add i t i ves t h a t a re used f requen t l y f o r immobi l iz ing organic contaminants. ac t i va ted carbon and mod i f ied c lays. Por t land cement do a poor j o b o f i nmob i l i z i ng organics, w i th the except ion o f h i g h l y po la r compounds i n low-to-moderate concentrat ions.

con ta in ing s i g n i f i c a n t concentrat ions o f organic contaminants, t h e r e a re a number o f issues t h a t should be examined, as discussed i n d e t a i l i n Sec- t i o n 4.4. F i r s t and foremost i s whether a des t ruc t i on o r e x t r a c t i o n technology i s a v a i l a b l e and app l icab le t o the waste. approximately equal, des t ruc t i on o r e x t r a c t i o n technologies are p re fe r red t o S/S because they e l im ina te o r remove the contaminant as opposed t o j u s t immobi l iz ing it. t h a t S/S i s the p re fe r red approach f o r wastes conta in ing organic Contaminants are: (a) t h e v o l a t i l i t y o f the organics and whether a i r emissions may occur

du r ing excavation, mixing, and/or cur ing; (b) the s o l u b i l i t y o f t he organics i n water and the meaningfulness o f conducting aqueous leach t e s t s as a measure o f t he degree o f immobi l i za t ion o f t he organics by S/S treatment; and (c) whether the organic contaminants may degrade o r t ransform t o o the r by- products du r ing S/S treatment and the t o x i c i t y o f those by-products.

Sect ion 4.2.2.2

These inc lude such ma te r ia l s as I n general, gener ic b inders such as

When eva lua t ing the f e a s i b i l i t y o f apply ing S/S technology t o wastes

A l l o ther f a c t o r s be ing

Other issues t h a t should be considered before conclud ing

2.5.2.4 C o m p a t i b i l i t y w i t h t h e Disposal o r Reuse Environment

The u l t i m a t e planned use o f t h e S/S-treated waste has a bear ing on b inder se lec t ion . municipal l a n d f i l l , m o n o f i l l , o r some other subsurface b u r i a l s i t e , o thers may

be reused as f i l l , road base, o r cons t ruc t ion mater ia l . For s t i l l o thers, t h e

Although many t rea ted wastes may be disposed o f i n a

2-59

method of treatment will be direct incorporation of the untreated waste, such as sandblasting grit, into a composite, such as asphalt. Numerous disposal and/or reuse options exist, but these are constrained by legal and institutional concerns. Reuse options, as opposed to disposal options, are nonrout- ine and subject to intense scrutiny to demonstrate environmental protection. Ultimate use options need to be anticipated and factored into the binder screening process along with product compatibility considerations.

For example, if the waste disposal location lies in the saturated zone, binder selection must consider the probability of water reaching the waste. Low permeability, adequate compressive strength, and stability in the groundwater geochemical environment will be important criteria. Also, engineering controls of disposal site hydrogeology may be incorporated to supplement binder performance criteria. Waste disposal site and waste performance considerations all relate to the protection of public health and the environment.

2.5.2.5 C o s t

Cost is an additional binder screening criterion, although this

Because economic criterion should be applied only after the interference, chemistry, and disposal /reuse environment issues have been considered. considerations are secondary to performance considerations, cost should be used only to screen binders that are significantly less economical or whose benefits clearly do not justify the added expenditure.

2.5.2.6 Process Track Record

Finally, process track record may be a discriminating factor in the selection of binders for bench-scale testing. developed that may be referred to as sources of information on successful treatability studies. Conner (1990) contains numerous tab1 es of performance data from previous treatability studies, organized by metal. (1991a) contains, on a disk in PC-DOS spreadsheet format, a tabulation of more than 2,500 performance data from S/S treatability studies. be sorted by metal, waste type, binder type, or other delineators. however, that published performance data from previous treatability studies generally are of limited value in designing future treatability studies

Several databases have been

Means et al.

The database can Note,

2-60

0

a

a

because seldom do those pub l ica t ions prov ide the l e v e l o f d e t a i l necessary t o permit r e p l i c a t i o n o f the experiment. Also, sub t le v a r i a t i o n s i n waste chemistry can lead t o very d i f f e r e n t t r e a t a b i l i t y r e s u l t s .

se lec t b inders f o r bench-scale tes t i ng , i t s i nc lus ion here i s n o t intended t o discourage the use o f innovat ive o r experimental b inders o r S/S technology, which may prove very usefu l i n c e r t a i n circumstances.

Although process t r a c k record may be one o f the f a c t o r s used t o

2.6 LABORATORY BENCH-SCALE SCREENING OF THE UASTE/BINDER MIXTURES

2.6.1 Purpose

The r e s u l t o f t h e waste/binder c o m p a t i b i l i t y l i t e r a t u r e screening descr ibed i n Sect ion 2.5 w i l l be a l i s t o f b inders o r b inder a d d i t i v e systems t h a t a r e promising candidates f o r S/S treatment. i d e n t i f i e d , then it should be tested as descr ibed i n t h i s sec t i on t o determine whether i t has mer i t ; otherwise i t w i l l be necessary t o i d e n t i f y an a l te rna- t i v e binder.

l i t e r a t u r e review and gener ic in fo rmat ion f r o m previous S/S pro jec ts , t he analys is now needs t o be made s p e c i f i c t o the actual waste being studied. Waste/binder mixes should be tes ted i n the l abo ra to ry t o determine r e l a t i v e performance. Because a n a l y t i c a l t e s t i n g i s expensive, i t i s imprac t i ca l t o conduct a f u l l set o f performance t e s t s on a l l o f t he waste/binder mixtures. Therefore, the t e s t i n g a t t h i s stage takes the fo rm o f "screening" as opposed t o de ta i l ed performance t e s t i n g and i s l i m i t e d t o the minimum requ i red t o i n d i c a t e process a p p l i c a b i l i t y .

t i a l l y equates t o the 'remedy se lec t ion" screening step i n U.S. EPA's guidance fo r t r e a t a b i l i t y t e s t i n g under CERCLA (U.S. EPA, 1989e). Note that for c e r t a i n S/S pro jec ts , where there i s a h igh l e v e l o f confidence t h a t a g iven b inder w i l l e a s i l y s a t i s f y the p r o j e c t ' s performance goals, t h i s bench-scale screening step may be deemed unnecessary. t i o n s where waste p roper t ies are simple and s t ra igh t fo rward , and where t h e selected b inder has a demonstrated t r a c k record f o r t he waste being s tab i - l i zed . However, because of the numerous poss ib le s u b t l e t i e s i n S/S process implementation and the poss ib le e f f e c t s o f s i t e - s p e c i f i c water p roper t i es on

I f on ly one b inder i s

Because the technology screening t o t h i s p o i n t has been based on the

The bench-scale screening process descr ibed i n Sect ion 2.6 essen-

This might be the case i n s i t u a -

2-61

b inder performance, i t i s h i g h l y reconmended t h a t bench-scale screening be conducted whenever possible.

r i z e d i n F igure 2-7. As t h i s f i g u r e ind icates, several i t e r a t i o n s may be necessary. Candidate binders i d e n t i f i e d f r o m Sect ion 2.5 a re screened us ing simple bench-scale t r e a t a b i l i t y t es ts . d isc r im ina te s u f f i c i e n t l y among binders, then add i t i ona l screening c r i t e r i a , such as ease o f implementation i n the f i e l d and cost, a lso may be considered a t t h i s stage. The b inder o r b inder system t h a t i s u l t i m a t e l y se lected w i l l undergo more thorough bench-scale performance t e s t i n g as descr ibed i n Sect ion 2.7.

The general steps o f t he bench-scale screening process are sumna-

I f the performance da ta do no t

2.6.2 Approach

Bench-scale screening e n t a i l s mix ing r e l a t i v e l y small amounts o f waste w i t h b inders f o r t e s t i n g i n d i v i d u a l parameters o r i n d i c a t o r s o f S/S technology performance. These labora tory tests , which are used t o determine whether the "chemistry" of the process works, are usua l l y performed i n batch

(e.g., " j a r t e s t s " ) w i t h t reatment parameters var ied one a t a time. Because small volumes and inexpensive reac tors such as b o t t l e s o r beakers are used, bench-scale screening t e s t s can be an economical way t o t e s t a r e l a t i v e l y l a r g e number o f performance and chemistry var iab les. evaluate a t reatment t r a i n made up o f several technologies and t o generate l i m i t e d amounts o f res idua ls f o r evaluat ion.

2.6.2.1 Experimental Design

I t i s a lso poss ib le t o

A t t he screening stage a l a r g e number o f t reatment op t ions are poss ib le . For t h i s reason, i t i s important t o e f f i c i e n t l y design the laboratory experiments. The important experimental questions t o be answered can genera l l y be expressed as hypotheses t h a t are supported o r disproved based on the experimental data. Decisions about how many and what k inds o f da ta t o measure are made most r e l i a b l y on the bas is o f s t a t i s t i c a l experimental design procedures used t o reduce the e f f e c t s o f experimental e r r o r s i n the measured data. and Cox, 1957; Hicks, 1973). The s i x fundamental steps i n developing a s t a t i s t i c a l experimental design a r e as fo l lows:

The area o f experimental design has been we l l developed (e.g., Cochran

2-62 ~

sectkn 2 8

FIGURE 2-7. LABORATORY SCREENING OF WASTE/BINDER MIXTURES

2-63

1. Clearly define the experimental objectives along with the tests to be performed.

2. Define the experimental factors to be controlled, as well as the levels and combinations of these factors to be investigated.

3. Establish the method of randomization to be used.

4. Select a statistical model to describe the experiment.

5. Specify the data analysis procedures to be employed as well as the desired statistical properties.

6. Select the experimental design parameters to achieve the desired statistical properties.

2.6.2.2 Performance Testing

Bench-scale screening is performed at this stage to comparatively evaluate the candidate binding agents. analytical data are not needed. concern, one or two simple performance tests, such as the frequently recommended TCLP and unconfined compressive strength (UCS) tests, should suffice for screening. because, compared to other leaching tests, it is relatively simple and inexpensive to perform. reuse options for S/S-treated waste will have some level of UCS performance standards. However, situations may be encountered where the use of other screening tests is justified.

different binder/waste ratios, because an optimal ratio cannot be determined a priori. binder may be rejected from further consideration because it was tested at the wrong proportion(s). 0.1, 0.3, and 0.6 based on dry weight (Barth and McCandless, 1989). These are probably appropriate for most generic binders. However, specialty binders may operate optimally at other ratios. variable at this stage, then three variations will yield the necessary data

As previously indicated, extensive Depending on the performance criteria of

The TCLP is recommended because of its regulatory status and

The UCS test is recommended because most disposal and

For example, 50 psi is typical guidance per U.S. EPA (1986b).

Testing methods are discussed in Chapter 3. It may be appropriate at this stage to test the effectiveness o f

If the binder/waste ratio is not treated as a variable, some useful

One test facility typically uses binder/waste ratios of

If the binder/waste ratio is treated as a

2-64

f o r most cases. More o r fewer binder/waste r a t i o s may be needed depending on factors such as waste complexity and t o x i c i t y . However, f o r CERCLA remedial act ions, i t r a r e l y i s wor thwhi le t o t e s t a t binder:waste r a t i o s g rea te r than 1.0, because of chemical cos ts and the d isposal compl icat ions presented by the volume expansion o f t h e waste a t t he h igher r a t i o s . Higher r a t i o s may be useful if b l a s t furnace s lag o r k i l n dust are ava i l ab le o r i f h igher water contents requ i re h igher b inder add i t ion .

should s a t i s f y the c r i t e r i a w i t h some margin o f sa fe ty because t h e l abo ra to ry i s a more c o n t r o l l e d environment than the f i e l d f o r t e s t i n g . ingred ien t p ropor t ions and the thoroughness o f mix ing are more var iab le . Typica l guidance f o r t he extent o f t h i s margin o f sa fe ty i s that the pe r fo r - mance c r i t e r i a should be s a t i s f i e d by a t l e a s t a f a c t o r o f 2. TCLP-tested Pb should be < 2.5 mg/L, versus the U.S. EPA th resho ld o f 5.0 mg/L. Th is i s techn ica l guidance, n o t po l i cy .

If screening t e s t s f a i l t o d i sc r im ina te s u f f i c i e n t l y among t h e bind- e r s (i-e., t hey perform s i m i l a r l y ) , then i t may be appropr ia te t o screen t h e b inders based on o ther fac to rs , such as ease o f f i e l d a p p l i c a t i o n (implenenta- b i l i t y ) o r cos t . Ease o f app l i ca t i on i n t h e f i e l d r e f e r s t o process complex- i t y o r s e n s i t i v i t y o f performance t o process parameters. processes, such as numerous sequential s teps and processes t h a t a re extremely s e n s i t i v e t o process parameters, such as exact ingred ien t p ropor t ions and thorough mixing, may be very d i f f i c u l t t o implement i n the f i e l d and probably should no t be attempted unless preceded by a p i l o t - o r f u l l - s c a l e demonstra- t i o n . a lso a f f e c t t h e ease o f using a p a r t i c u l a r S/S process a t a p a r t i c u l a r s i t e . Both the S/S f i e l d equipment necessary and treatment chemicals used should be conducive t o safe and e f f i c i e n t a p p l i c a t i o n under actual f i e l d condi t ions.

I f a l l o the r f a c t o r s (performance and implementabi l i ty ) are equal, then cos t may be used t o s e l e c t a binder. equipment r e n t a l s o r use rates, and labor . information a re d i f f i c u l t t o est imate a t t h i s stage. However i t should be poss ib le t o develop a sense f o r the ove ra l l process complexity and maximum poss ib le processing ra te . S/S treatment i s prov ided i n Sect ion 4.10.

Whatever performance c r i t e r i a a re chosen f o r t es t i ng , t h e waste

I n t h e f i e l d ,

For example,

H igh ly complex

Heal th and sa fe ty considerat ions f o r workers and nearby i nhab i tan ts

A f i n a l f a c t o r a f fect ing b inder screening i s cost.

The most s i g n i f i c a n t cos t items are usua l l y chemicals, The l a t t e r two categor ies o f cos t

Add i t iona l in fo rmat ion pe r ta in ing t o t h e cos t o f

2-65

e 2.6.3 Technical Guidance

Guidance for bench-scale binder screening is sunmarized in Table This information is provided to assist in planning and implementing 2-12.

valid bench-scale screening tests for S/S.

2.7 BENCH-SCALE PERFORMANCE TESTING/PROCESS OPTIIIUTIOW

2.7.1 PurDose and Objectives

At this stage in the S/S treatability study, limited treatability testing has been conducted and a promising binder has been identified. Now it is necessary to demonstrate that the binder will achieve all relevant project performance goals and to optimize the S/S process in terms of design, field implementability, and cost performance. This step in the treatability study is referred to herein as "bench-scale performance testing/process optimization" and equates to the "remedy design testing" step in U.S. EPA's guidance for performing treatability studies under CERCLA (U.S. EPA, 1989e). Bench- scale performance or remedy design testing is frequently performed soon after the Record of Decision in CERCLA projects, prior to implementing the remedy.

A descriptive performance testing protocol that will satisfy the requirements of all S/S projects cannot be specified because site-specific projects have different performance goals and because the response of individual wastes to S/S technology can be unpredictable. In the absence of extensive regulatory requirements for S/S treatment projects, acceptance criteria must be determined largely on a case-by-case basis. The approach summarized here and illustrated in Figure 2-8 advocates that the level of performance testing be set by the potential level o f risk posed to human health and the environment. That is, the testing program should be based upon the guiding principles derived from the ultimate risk posed by the waste in its planned disposal or reuse environment.

Four principal factors affect risk in this context:

Waste volume

Type and concentration of contaminants (metals, organics, or both)

2-66 I

TABLE 2-12. BENCH-SCALE BINDER SCREENING GUIDANCE

~

1. Test the effectiveness of any pretreatment system.

2. Screen at least two to four binders at two or more binder/waste ratios.

3.

4.

Ensure there are no binder/waste incompatibilities that could pose a safety hazard (release of toxic gas, etc.).

Use process, waste, and binder information to determine whether to base testing on composited waste samples, worst-case samples, or both.

5. Carefully monitor, control, and record binder additions, order and sequence of additions, timing, and other procedural information.

6. Conduct several rounds of bench-scale testing to optimize binder performance.

7. The chemical compositions of the binder and binder additives should be known or chemically analyzed to ensure that these ingredients do not contain hazardous constituents or properties. Consult MSDSs at a minimum.

New ARARs may be developed as a result of the binder and/or binder additives (e.g., dust emissions, corrosivity [pH] limits, etc.).

Have the treatability study witnessed by an independent third party or regulatory agency for impartiality.

Simulate anticipated field conditions during curing as closely as possible (e.g., do not necessarily put the treated waste imediately into a sample jar).

11. Allow the sample to cure properly before chemical and physical analyses.

12. Calculate the percent reduction in TCLP contaminant concentration caused by stabilization both with and without the effects of waste dilution by binder ingredients.

13. Test the most critical ARARs (e.g., leaching characteristics and critical chemicallphysical properties).

14. Assess air emissions if volatile organics are present.

8.

9.

10.

15. Send splits of a few samples to a second laboratory verification.

for interlaboratory

16. Conduct the bench-scale screening project under a proper QA/QC program, including statistical design, replication, blind controls, compliance with laboratory certification requirements, etc.

Calculate or measure waste volume increase from binder/water additions. 17.

2-67

sectla, 27.1

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FIGURE 2-8. BENCH-SCALE PERFORMANCE TESTING OF SELECTED WASTE/BINDER MIXTURES

2-68

I .

S i t e c h a r a c t e r i s t i c s o f t he planned disposal o r reuse

Demonstrated performance o f the S/S process

environment

se lected

This sec t ion prov ides q u a l i t a t i v e guidance f o r determin ing t h e l e v e l o f r i s k based on the above categor ies o f fac to rs . The l e v e l o f r i s k then determines t h e general ex ten t o f recommended performance t e s t i n g . More extens ive t e s t i n g requirements are requi red f o r p ro jec ts t h a t present g rea te r r i s k i n order t o increase the l e v e l o f confidence t h a t t he t rea ted waste w i l l remain s tab le f o r the l ong term. One type o f t e s t i n g requirement t h a t i s not der ived from r i s k pe r ta ins t o s p e c i f i c binders. eva lua t ion i s discussed b r i e f l y i n Sect ion 2.7.2.3.

t i o n are t o demonstrate t h a t the S/S-treated waste i s :

Test ing r e l a t e d t o b inder

The goals of bench-scale performance t e s t i n g and process opt imiza-

Chemically and phys i ca l l y s tab le ( i . e . , no f r e e l i q u i d s as determined by the p a i n t f i l t e r tes t , low leaching rates)

Compatible w i t h i t s disposal o r reuse environment (e.g., possesses adequate compressive strength, i s nonbiodegradable, and has s u f f i c i e n t l y l o w permeab i l i t y )

I n conformance with the ARARs by an adequate margin o f sa fe ty

techno1 ogies

the f i e l d

Cost -e f fec t i ve compared w i t h other poss ib le t reatment

Demonstrated e f f e c t i v e and r e a d i l y implementable i n

Generalized procedures and ra t i ona les f o r determining the l e v e l o f performance t e s t i n g are provided i n the fo l l ow ing sections. t h i s approach appl ies mainly t o p ro jec ts under CERCLA remediat ion and RCRA placement. As ind i ca ted i n Sect ion 2.3, the t e s t i n g requirements o f a RCRA TSD f a c i l i t y are more s p e c i f i c and inc lude the Paint F i l t e r Test f o r f r e e l i q u i d s , the TCLP f o r leachable m e t a l s , and the other th ree t e s t s f o r hazardous waste c h a r a c t e r i s t i c s (i .e., i g n i t a b i l i t y , c o r r o s i v i t y , and r e a c t i v i t y ) .

Please note t h a t

2-69

2.7.2 How Much Performance TestinQ?

2.7.2.1 Levels o f R i s k

R isk determinat ion i s probably equivocal i n most cases, and excep- t i o n s t o any approach w i l l always be i den t i f i ed . No exper t system e x i s t s y e t f o r determining r i s k as i t r e l a t e s t o S/S p ro jec ts . One approach, however, i s based on the p r i n c i p a l r i s k f a c t o r s i d e n t i f i e d i n Table 2-13. Th is s i m p l i f i e d approach i s provided as rule-of-thumb guidance only. As i n d i c a t e d prev ious ly , numerous exceptions a re l i k e l y t o e x i s t .

The ca tegor ies o f r i s k i n Table 2-13 are (a) waste volume, (b) t y p e and quan t i t y o f metal contaminants, (c) type and quan t i t y o f o rgan ic contaminants, (d) s i t e (d isposal o r reuse) cha rac te r i s t i cs , and (e) demonstrated e f fec - t iveness o f t he S/S process. Each o f these r i s k categor ies i s subdivided i n t o low, medium, o r h igh r i s k l eve l s . Examples o f each are g i ven i n Table 2-13. The t rends are s t ra igh t fo rward . Larger volumes o f waste, h ighe r hazard contaminants, s i t e cond i t ions promoting poss ib le exposure t o human o r eco log ica l recep- to rs , and undemonstrated S/S processes are a l l associated w i t h h igher r i s k and the re fo re h igher l e v e l s o f performance t e s t i n g . Metals and organics a re con- s idered separately, because a waste conta in ing both i s more d i f f i c u l t t o t r e a t and the re fo re poses grea ter r i s k than a waste conta in ing o n l y one o r t he o ther . Table 2-13 shows where a p r o j e c t f a l l s among the f i v e r i s k f a c t o r s and i s used t o determine the necessary l e v e l o f performance tes t i ng , which i s expla ined f u r t h e r i n Sect ion 2.7.2.2. I d e n t i f y i n g the l e v e l o f r i s k i s a sub jec t i ve determinat ion on the p a r t o f the p a r t i c i p a n t s i n the t r e a t a b i l i t y study.

2.7.2.2 Levels o f Performance Tes t ing

Three l e v e l s o f performance t e s t i n g correspond t o t h e th ree l e v e l s Table 2-14 describes some t y p i c a l t e s t i n g requ i re - o f r i s k from Table 2-13.

ments ( leaching, phys ica l , and o ther chemical t e s t s ) f o r each o f the t h r e e l eve l s . The t e s t s t o be run cannot be spec i f i ed exact ly , as they w i l l depend upon the needs o f t he i n d i v i d u a l S/S pro jec t . For example, a freeze/thaw t e s t may not make sense f o r an S/S-treated waste placed e n t i r e l y below t h e f r o s t l i n e . f a r above t h e groundwater tab le. Thus, Table 2-14 prov ides guidance on t h e o v e r a l l magnitude or l e v e l o f e f f o r t associated w i t h t h e t e s t i n g program as opposed t o s p e c i f i c t e s t i n g requirements.

Permeabi l i ty would be o f l i t t l e consequence f o r d isposal i n the dese r t

2-70

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A

2.7.2.3 Tests f o r S p e c i f i c B ind ing Agents

Binder se lec t i on i s an add i t i ona l cons iderat ion i n des ign ing the performance t e s t i n g program. s p e c i f i c p roper t ies o f the b inder than t o the r i s k associated w i t h waste chemistry and s i t e cha rac te r i s t i cs .

Cer ta in types o f t e s t s r e l a t e more t o the

Examples inc lude the fo l low ing :

When s u l f i d e i s used as a t reatment chemical, pH and reac t i ve s u l f i d e analyses ( o r s u l f i d e r e a c t i v i t y , t he so-cal led "Claussen t e s t " ) should be conducted t o ensure t h a t the waste meets the RCRA c o r r o s i v i t y (pH less than 12.5) and reac t i ve su l f i de ( l ess than 500 mg/kg) guide1 ines.

When thermoplast ics or o ther organic binders a re used, biodegradat ion t e s t s may be required.

In some s i tua t i ons , a t e s t method may need t o be mod i f ied t o accommodate a s p e c i f i c S/S-treated waste. F a r example, because the o i l s and bitumens i n asphal ts would probably lead t o f i l t e r plugging, the f i l t r a t i o n procedures may need t o be modi f ied o r e l iminated completely.

2.7.2.4 Acceptance C r i t e r i a

The success o f the t r e a t a b i l i t y study w i l l be measured i n terms o f whether the t e s t s s a t i s f y predetermined performance ob jec t ives . c r i t e r i a are regu la to ry l i m i t s , such as the m e t a l thresholds t h a t have been es tab l i shed f o r the TCLP, EP Tox, and C a l i f o r n i a Waste Ex t rac t i on Test (WET).

Some o f these

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However, most c r i t e r i a a re n o t s t r i c t regu la to ry l i m i t s and must be determined on a case-by-case bas is . c r i t e r i a w i l l vary w i t h the s i t e c h a r a c t e r i s t i c s o f t h e d isposal environment. Permeabi l i ty requirements w i l l va ry w i t h t h e water f l u x through the d isposal zone and t h e p rox im i t y t o the groundwater tab le . The UCS c r i t e r i a should be based on an engineering c a l c u l a t i o n o f the l o a d under which t h e waste w i l l be placed p l u s a sa fe ty fac to r .

es designing t o t h e needs o f the i n d i v i d u a l p ro jec t . t o design ove r l y r e s t r i c t i v e c r i t e r i a . adequate t o ensure, w i t h an acceptable degree o f p r o b a b i l i t y , t h a t t he S/S- t r ea ted waste w i l l perform s a t i s f a c t o r i l y i n the f i e l d .

ob jec t i ves are n o t sa t i s f i ed ) , then several op t ions are ava i lab le , f o r example:

For example, t he t a r g e t permeab i l i t y and UCS

The approach for determin ing acceptance c r i t e r i a genera l l y emphasiz- I t i s n o t c o s t - e f f e c t i v e

However, t h e c r i t e r i a need t o be

I f the t r e a t a b i l i t y s tudy i s unsuccessful (i.e., i f some performance

. Revise the performance ob jec t i ves w i t h i n regu la to ry

Modify t h e formulat ions

Inves t i ga te a completely d i f f e r e n t b inde r system

Add more engineering con t ro l s t o the f i n a l placement l o c a t i o n

l i m i t a t i o n s ( f o r example, exception t o ARARs)

Most performance de fec ts i d e n t i f i e d i n t r e a t a b i l i t y s tud ie c n be corrected by process o r b inder mod i f i ca t ions . treatment system may be complex o r expensive. f a c t o r y t h a t S/S i s n o t a v i a b l e option, then the S/S t r e a t a b i l i t y study i s concl uded.

However, the r e s u l t i n g S/S I f performance i s so unsat is-

2.7.2.5 Process Optimization

The bench-scale t r e a t a b i l i t y environment o f f e r s an exce l l en t oppor tun i t y t o f ine- tune the S/S process f o r s i t e - s p e c i f i c waste. op t im iza t i on inc ludes the fo l l ow ing types o f a c t i v i t i e s :

Process

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Determining the trade-offs between reducing the binder:waste ratio and associated cost savings versus process performance

additives in terms of processing rate and process performance

slight variations in binder amounts, curing conditions, and/or mixing efficiency

Evaluating the sensitivity of the S/S process to expected variations in waste properties (average vs. worst-case contaminant concentrations, variable matrix properties, etc.)

Determining the optimal sequence of binder or

Evaluating the sensitivity of the S/S process to

Process optimization is an important step in maximizing cost- effectiveness and determining process sensitivities.

2.7.3 Technical Buidance

Guidance for conducting bench-scale performance testing is provided in Table 2-15. appl icabl e.

The guidance provided in Section 2.6 (Table 2-12) is also

2.8 PILOT-SCALE AND FIELD DEHONSTRATIONS

2.8.1 The Need f o r Process Scale-up

Bench-scale treatability testing ends when a suitable binder and binder:waste ratio is selected. test or field demonstration test o f the stabilization process is necessary prior to a full-scale cleanup. ate-scale simulation (often in the laboratory) of a full-scale operation. Field demonstration generally refers to a simulation of the full-scale operation conducted on-site with actual full-scale (or close to full-scale) equipment. A pilot or field test may be needed to build confidence in the binder selection or to gather data for design of the full-scale system. Pilot-scale studies are typically directed at resolving equipment sizing, selection, or scale-up issues. Usually in S/S technology, the field test is a dry-run of the full-scale treatment equipment under carefully monitored conditions prior to proceeding with full-scale treatment.

The user must then determine whether a pilot

A pilot test generally refers to an intermedi-

The expense of a

I

TABLE 2-15. GUIDANCE FOR BENCH-SCALE PERFORMANCE TESTING

1. The same guide1 ines concerning procedures f o r conducting bench-scale t r e a t a b i l i t y t e s t s provided under sec t ion 2.6 (Table 2-11) a l so apply here.

2. Performance t e s t s are needed f o r a l l ARARs, f o r example:

a.

b.

C.

d.

e.

f.

9.

h.

i.

3.

I f subsurface disposal i s planned, appropr ia te t e s t s should be conducted (e.g., unconfined compressive s t rength and permeab i l i t y , e t c ) .

I f surface o r near-surface d isposal i s planned, appropr ia te t e s t s should be conducted (e.g., wet/dry, freeze/thaw, etc . ) .

Long-term s t a b i l i t y needs t o be ensured. The TCLP i s n o t s u f f i c i e n t evidence o f long-term s t a b i l i t y . be conducted t h a t b e t t e r address long-term s t a b i l i t y (see Sect ion 3.2) and/or the TCLP should be conducted on t rea ted waste a f t e r d i f f e r e n t cur ing per iods (Sect ion 4.7).

For wastes having organic contaminants with low aqueous s o l u b i l i t i e s , leaching w i t h an organic so lvent may be appropr ia te (see Sect ion 4.4.3).

For wastes conta in ing organic Contaminants, conduct a mass balance t o account f o r the f r a c t i o n s o f contaminants t h a t are leachable, immobile, and released due t o v o l a t i l i z a t i o n .

Fo r a suspected c o l l o i d a l contaminant t ranspor t mechanism, consider s u b s t i t u t i n g l a rge r pore-size f i l t e r medium f o r the standard f i l t r a t i o n medium o r using c e n t r i f u g a t i o n instead o f f i l t r a t i o n .

Leach t e s t s using s i t e - s p e c i f i c groundwater (as opposed t o gener ic leachate o r d i s t i l l e d w a t e r ) may be appropr iate.

I f the b inder i s biodegradable, a biodegradat ion performance t e s t should be conducted.

I f the disposal s i t e cou ld leach i n t o an aquat ic system, leachate bioassay may be appropr iate.

Note t h a t t he binders themselves may conta in contaminants such as metals; these should be taken i n t o considerat ion i n performance tes t i ng .

A l t e r n a t i v e leaching t e s t s should

3.

4 .

A t o t a l contaminant analys is should genera l l y be performed on t h e same subsample used f o r leach t e s t s t o e l im ina te f a l s e negatives.

The leaching performance da ta should be corrected f o r t he e f f e c t o f d i l u t i o n t o determine the actual ex ten t o f s t a b i l i z a t i o n due t o binding.

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TABLE 2-15. GUIDANCE FOR BENCH-SCALE PERFORMANCE TESTING (Continued)

5.

6.

7.

8.

9 .

10.

11.

12.

13.

Simulate field conditions as closely as possible during curing.

Allow the waste to cure for an appropriate period of time before anal ysi s.

The entire performance testing program should be conducted under an appropriate QA/QC program, including statistical design, rep1 icates, analytical methods, blind controls, and other controls.

There should be a safety margin in the performance data relative to the numerical thresholds because the S/S process may not work as well as in the field.

The S/S process developed and demonstrated at this stage must be implementable in the field (i.e., not too complex).

The volumetric expansion of the waste during treatment must conform to the disposal space constraints.

The cost should be realistic for an S/S treatment option; depending on the circumstances, a realistic cost is usually less than S150/ton.

Splits of some proportion of the samples should be sent to a second analytical laboratory for interlaboratory comparison.

It is advisable for bench-scale testing to be observed by an independent third party or regulatory agency for impartiality.

pilot-scale (intermediate-scale) test is usually not warranted, except for very complex S/S projects.

The decision whether to do a pilot or field test hinges mainly on how widely a particular waste/binder system has been demonstrated in the past. Other factors such as regulatory requirements, full-scale equipment design, and cost estimation are also considered. If treatability testing shows that the waste contains common forms of contaminants that respond well to stabilization in a matrix that contains no significant amounts of interferants, and if the binder system is well-demonstrated and commonly used on these contaminants, then a pilot or field demonstration may not be necessary. If the contaminant species i s complexed in the waste matrix, if the waste contains interferants, or if a not-so-well-understood binder system i s being used, a pilot or field-scale demonstration is advisable to ensure the effectiveness of

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t he process. As i nd i ca ted above, a f i e l d demonstration can be conducted simply as a d i sc re te p a r t o f t he f u l l - s c a l e cleanup, with a pause a f t e r t he demonstration t o evaluate e f fec t i veness and/or a l low f o r regu la to ry review. Th is i s a use fu l step f o r c a l i b r a t i n g mater ia l f l o w r a t e s and f o r determining optimal processing ra tes . i d e n t i f i e d and corrected, and f i e l d personnel can be t r a i n e d i n t h e sa fe operat ion o f the f u l l - s c a l e equipment. Once the S/S process has been demon- s t r a t e d i n the f i e l d , t he cleanup can cont inue w i t h the same equipment.

Safety problems can a l so be i d e n t i f i e d du r ing p i l o t / f i e l d tes t i ng . For example, t he Handbook f o r Stabilization/Solidification o f Hazardous Waste (U.S. EPA, 1986c) descr ibes how r a p i d add i t i on o f a r e a c t i v e s t a b i l i z a t i o n agent (e.g., unhydrated l ime) can cause r a p i d v o l a t i l i z a t i o n o f lower b o i l i n g - p o i n t organics, lead ing t o f l a s h f i r e s .

A s p e c i f i c case h i s t o r y demonstrates t h e a d v i s a b i l i t y o f a f i e l d t e s t p r i o r t o f u l l - s c a l e treatment. Physical cond i t ions du r ing f u l l - s c a l e cleanup may vary from those i n the l abo ra to ry so as t o a l t e r o r prevent t he des i red reac t ions o f t h e s t a b i l i z a t i o n process. A case i n p o i n t i s described by Means e t a l . (1991b) f o r a f i e l d demonstration s t a b i l i z i n g sand b l a s t i n g g r i t con ta in ing copper and lead as contaminants. A laboratory-proven b inder system composed o f s u l f i d e and f l y ash was used du r ing the i n i t i a l demonstra- t i o n . The t rea ted waste was s to red i n the open on p l a s t i c sheets f o r cur ing. Samples o f t he cured waste showed t h a t the waste a t t he top o f t he p i l e was

no t as w e l l s t a b i l i z e d as the waste a t t he bottom o f t h e p i l e . During f u r t h e r t r e a t a b i l i t y tes t ing , i t was discovered t h a t when t h e waste was cured i n a j a r , s t a b i l i z a t i o n was e f f e c t i v e . i n c l i n e i n t h e open a i r , s imu la t ing the f i e l d waste ma te r ia l , some excess s t a b i l i z a t i o n reagent was observed d ra in ing o f f the waste mater ia l . concluded t h a t environmental cond i t ions caused by p i l i n g were prevent ing t h e reac t i on between the s u l f i d e and the metal ions from reaching completion. Thus, the f i e l d system was shown t o be not as e f f e c t i v e as the bench-scale system f o r t h i s s t a b i l i z a t i o n pro jec t . Fortunately, t h e problem was i d e n t i - f i e d and cor rec ted a t an e a r l y stage o f f i e l d treatment.

A l l the f a c t o r s mentioned above should be taken i n t o cons idera t ion i n determin ing the need f o r a f i e l d demonstration be fore f u l l - s c a l e cleanup. Once a dec i s ion i s made t o proceed w i t h the demonstration, t he steps i n the f lowchart o f F igure 2-9 may be fol lowed. Two t o f o u r small batches o f waste

Any de f i c ienc ies i n the f i e l d equipment can be

When the waste was cured on a gen t le

I t was

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Study Results

t No

Run 2 to 4 Smafl Batches of Waste on the Piiot/Field

Equipment

Samples to Evaluate Critical Performance

Proceed With Full-Scale

Remediation

Change Equipment or Engineering Parameters or

Reformulate Binder -

FIGURE 2-9. PILOT-SCALE TEST SCREENING

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0

a

a

are typically r u n , with 1 t o 15 cubic yards o f untreated waste material per batch generally used depending on the s ize o f the available equipment. S t a t i s t i ca l ly significant samples are taken and analyzed by the t e s t s described in Chapter 3 t o demonstrate effectiveness. procedures are followed during sample collection and analyses t o ensure re1 i abi 1 i ty.

analyzed and evaluated for c r i t i c a l performance goals as determined a t an ea r l i e r stage. I f the samples meet these performance objectives, the user may proceed w i t h the full-scale cleanup. If the samples f a i l the performance objectives, the user has t o determine whether the f ie ld-scale equipment, the binder formulation, and/or other engineering parameters (e.g., flow r a t e s , storage environment) are a t fau l t . t i f y the cause of the deviation between bench-scale and f ie ld-scale resu l t s .

Adequate quali ty assurance

After allowing t h e treated waste to cure, the samples can be

Further tes t ing may be necessary t o iden-

2.8.2 Scale-UP Issues ' Scale-up from a bench-scale t o f i e ld demonstration or fu l l - sca le

process generally focuses on the materials handl ing aspects of the process since t h e chemistry already has been addressed i n the bench-scale t e s t s . Scale-up plans should address each of the following wherever applicable:

Waste excavation for ex s i t u processes

Waste handl i ng

Equipment selection ii s i z i n g

Chemical reagents (binder) storage

Pretreatment of waste

Presence o f debris

Materi a1 s balance

Mixing and curing

Stabi 1 ized waste disposal

The most common methods of s tab i l iza t ion are plant mixing and i n s i t u mixing. Plant mixing involves removing the waste from i t s location and

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.

t r a n s f e r r i n g i t t o a t reatment p lan t . The waste i s mixed w i t h the s t a b i l i z a - t i o n agents i n the f i xed o r mobi le t reatment p lan t . t he waste remains i n place, and the s t a b i l i z a t i o n agents are i n j e c t e d o r mixed w i t h spec ia l i zed augers o r o ther equipment.

sludges o r semisol id wastes. t he disposal area and covered w i t h a l a y e r o f s t a b i l i z a t i o n agents. The laye rs a re l i f t e d and turned over repeatedly and then d r i e d and compacted. A top l aye r o f c lean s o i l i s then added as a cap. Yet another method, in-drum mixing, i s genera l l y used f o r h i g h l y t o x i c wastes i n drums. enough headspace above the waste i n the drum, s t a b i l i z a t i o n agents may be added and mixed w i t h the waste.

SITE demonstrations o f s t a b i l i z a t i o n techniques such as p l a n t mix ing (U.S. EPA 198911 and 19891) and i n s i t u s t a b i l i z a t i o n (U.S. EPA, 1989j). conta in important in fo rmat ion on f i e l d opera t ion and performance. The Handbook f o r Stabi7ization (U.S. EPA, 1986c) i s a l so a good reference, descr ib ing operat ing cha rac te r i s t i cs and cos t o f large-scale equipment.

ment f o l 1 ows.

2.8.2.1 Waste Excavation and Handling

During i n s i t u mixing,

Another method, area mixing, i s used main ly f o r t r e a t i n g o i l y I n t h i s method, a l a y e r o f waste i s p laced i n

I f there i s

The U.S. EPA publ ished several Technology Evaluat ion Reports on i t s

These repo r t s

a A discuss ion o f some commonly used f u l l - s c a l e s t a b i l i z a t i o n equip-

T rad i t i ona l earth-movi ng equipment (e.g., backhoes, drag1 ines , bul ldozers, f ront-end loaders) i s used f o r t h i s process. I f f r e e l i q u i d i s present on top o f the waste, i t may have t o be pumped out and t rea ted as a separate waste stream. enclosed o r provided w i t h breath ing apparatus i f a i r hazards are generated dur ing excavat ion.

Depending on the nature o f the waste and the s i t e , t he excavated

waste can be t ranspor ted t o the treatment p l a n t by a f i x e d system (conveyor o r screw auger), dump t r u c k ( f o r s o i l ) , pump and hose ( f o r l i q u i d s and sludges), or , i f the waste i s p a r t i c u l a r l y hazardous, i n drums. Sp i l l age should be avoided dur ing t ranspor t .

The equipment operator may have t o be completely

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2.8.2.2 Stabilizing Agent Storage

For cost-effective operation, it is important that sufficient amounts of chemicals be available to avoid project shut-down for restocking. Amounts required are determined from treatability testing results, specifically the binder:waste ratio. Bins, hoppers, and silos are used for storage of dry chemicals. If liquid chemicals are being used, liquid storage tanks or drums may be necessary. need to be replenished on a continuous basis during the project.

Unless the waste volume is small, chemicals generally

2.3.2.3 Pretreatment of Waste

Pretreatment may be necessary for (a) improving the material handling characteristics of the waste, (b) improving waste/binder compatibility, and (c) removing constituents that either interfere with or are not affected by S/S processing. (See Section 4.1.4). Pretreatment can sometimes also reduce the quantity of stabilization agents during mixing.

such as crushers (to remove large rocks or debris that may clog up the mixing equipment), drying or dewatering, blending and homogenization, pH adjustment, or heating to drive off volatiles. capture mechanism for the vapors may be necessary. screening may have to be treated separately or disposed of appropriately.

especially at sites where the waste is difficult to handle with standard earth-moving equipment. ion operation had to be temporarily abandoned because of problems at the pretreatment stage. with wet, sticky, or fine materials such as clay. Use o f vibratory screens or special crushers may be necessary.

2.8.2.4 Mixing and Curing

Pretreatment may include screening and/or size-reduction equipment

If volatiles are being driven off, some Oversize materials from

Pretreatment is important from a materials handling point of view,

There have been instances where the entire remediat-

Screens and crushers can easily get clogged, especially

L

Mixing is a critical step in ensuring good S/S process performance. All precautions must be taken to ensure that the waste and binder chemicals are mixed thoroughly and allowed to cure adequately. equipment is suitable for this application.

A wide range of mixing The choice o f equipment depends

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on t h e type o f waste/binder system and method o f s t a b i l i z a t i o n . simple and inexpensive s i t ua t i on , area mix ing can be done wi th a backhoe.

s t a b i l i z a t i o n agents i n t o the s o i l and t o cause a g i t a t i o n and mixing. Backhoes can be used as i n s i t u mixers, bu t the mix ing i s no t r e l i a b l e . Another i n s i t u process i s grout ing, whereby f l u i d s (usua l l y water and cement) a re i n j e c t e d i n t o the ground, where they are al lowed t o s e t i n place.

A range o f equipment, i nc lud ing pug m i l l s , ext ruders, r i b b o n blenders, sigma mixers, m u l l e r mixers, and screw conveyors i s ava i lab le . Standard construc- t i on - t ype cement o r concrete mixers and t rans i t -m ix t rucks have a lso been used. Mix ing can be done as e i t h e r a batch o r a continuous process. volumes o r weights o f waste and chemicals can be added w i t h reasonable accuracy i n t o the mixer by front-end loaders o r conveyors. can be metered and pumped in.

I f continuous operat ion i s desired, a l l m a t e r i a l s must be i n t roduced a t a c a r e f u l l y c o n t r o l l e d r a t e . hand l ing equipment such as l i ve-bo t tom feeders. Equipment such as pug m i l l s can f requen t l y be operated i n e i t h e r batch o r continuous mode. poss ib le t o use a pug m i l l i n batch mode du r ing p i l o t or f i e l d demonstrat ion and then change t o continuous mode w i t h several minor mod i f i ca t ions : t he angles on t h e paddles o r knives on the pug-mil l shaf t (s) , changing the l e v e l o f t he discharge gate, and/or changing the speed o f r o t a t i o n o f t h e screws. must be r e c a l i b r a t e d t o ensure t h a t the des i red residence t ime and mix ing are being achieved.

Cer ta in c lay- type s o i l s can become extremely s t i c k y and adhere t o the s h a f t and s ides o f t h e mixer, lead ing t o poor mix ing .

a l so be problemat ic i f t h e v i s c o s i t y o f the mix changes r a p i d l y du r ing s e t t i n g . amounts o f s t a b i l i z a t i o n agents needed. amounts o f chemicals requ i red f o r f u l l - s c a l e operat ion can be underestimated because l e s s than idea l mix ing e f f i c i e n c y was no t accounted fo r .

f o r t he e n t i r e s t a b i l i z a t i o n process.

I n t h e most

For i n s i t u mixing, spec ia l augers and d r i l l s a re used t o i n j e c t t h e

Plant mix ing provides the maximum c o n t r o l on t h e mix ing process.

Known

Water o r s l u r r i e s

This may requ i re spec ia l i zed ma te r ia l -

Thus, it i s

changing

However, when mixers are switched from batch t o continuous mode, they

Mix ing opt ions a lso depend on the type o f waste being mixed.

Obta in ing good m ix ing can

Mixer performance needs t o be evaluated i n order t o conf i rm t h e During bench-scale t e s t i n g , t h e

The s i z e o f t he mixer genera l l y determines the maximum throughput Mixers va ry w ide ly i n s ize, w i t h

2-84

achievable throughputs between 1 and 200 tons per hour. usually provides a greater throughput but at the possible expense of mixing efficiency. continuous processes.

standing piles. Controls should be implemented both to protect the surrounding environment from possible runoff or leaching from the curing waste and to protect the curing waste from wind and precipitation.

2.8.2.5 Stabilized Waste Disposal

Continuous processing

Two mixers can be used to improve mixing in high throughput

Curing of the waste can occur in either containers, pits, or free-

I

If the stabilized waste is to be used as fill, the use of standard earth-moving equipment (e.g., graders, bulldozers, front-end loaders) will usually suffice. After replacement, the waste i s compacted. The moisture content of the compacted material should be controlled to give the maximum density for a given material. The moisture-density relationship can be determined by the Proctor test (ASTM 0698). can be detrimental.

increase can be underestimated during bench-scale testing and should be re- established in the field.

Post-treatment controls (e.g., capping, slurry wall, soil cover) frequently accompany stabilization to effectively mitigate site-specific threats. Performance standards for caps are mentioned in 40 CFR 264.310 but may not always be appropriate. Final selection of capping materials and cap design depends on several factors such as climate, site hydrogeology, availability of materials, and regulatory requirements.

Too much or too little moisture

This volume Stabilization generally results in a volume increase.

2.8.3 Samplina and Analysis o f the Treated Waste

The guidance on sampling and analysis in Sections 2.2.1.2 and 2.2.3.3 has general applicability to the pilot or field demonstration as well. In situ projects pose special complications for verification testing. example, drilling or coring is required and homogeneity and setting rates are more difficult to assess. Analyses must be conducted to determine compliance with the performance goals of ARARs (Section 2.3) in a statistically significant manner.

For

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